I guess you could palindromically call me “IDDI”

I may be yellow; two-faced I be,
But you would be wise to never cross me.
I stand straight and tall; my authority's given.
You'd best follow me if you're want to stay livin'.

Don't
Cross
Me

Explain the above and show me my picture for acceptance.

Hint:

A number of answers are like signs pointing us in the right direction; a number are not.

It's all G
reek to me

Hint #2:

In this picture, the left side would be
ID
DI
but the right side would be
DI
ID

• They are both 'i"s. – Chowzen Apr 16 '18 at 12:29
• Is it a hint that "don't / cross / Me" is written on separate lines? – Ideogram Apr 18 '18 at 5:53
• @Ideogram It merely reemphasizes that I shouldn't be crossed (and maybe poetically supplies closure). – Chowzen Apr 18 '18 at 11:29
• I'm thinking it's some kind of road or warning sign from your last comment, but I'm not sure about cultural context since that could affect answers slightly. Pretty sure the "IDDI" part refers to "I didn't do it", though I'm not sure whether that applies to the sign or the person disobeying it... – Pleiades Apr 18 '18 at 15:06
• Can we get another hint? – Philip Holly Apr 25 '18 at 20:49

Is it a

Two way traffic sign?

I may be yellow; two-faced I be,

It is yellow, with arrows facing in two directions

But you would be wise to never cross me.

To cross can mean "to oppose openly", that wouldn't be a wise thing to do as you might run into oncoming traffic

I stand straight and tall; my authority's given.

It's a sign usually affixed to a straight and tall pole, and since it is a road sign, its authority is given by law

You'd best follow me if you're want to stay livin'.

Seems obvious, same as the second line, you might run into oncoming traffic if you don't follow the sign

Don't Cross Me

Is just reinforcing the message

Hint:

A number of answers are like signs pointing us in the right direction; a number are not. Probably refers to the answer being a "sign pointing us in the right direction".

It's all G
reek to me
Might refer to the title about palindromically calling it "IDDI" being far-fetched/hard to understand Refers to the fact that the sign is made up of iota's (Ι) and delta's (Δ) from the Greek alphabet.

Hint #2:

In this picture, the left side would be
ID
DI
but the right side would be
DI
ID
Seems to show to a road with directional lanes swapped from right to left, so the left side could be "Inverse (or Inverted) Direction" (which is the same as opposite direction), if left is the "Inverse Direction" (ID) then the right side would be palindromically be "Directionally Inverse" (DI) and vice-versa when the lanes are swapped. And yes it is far-fetched/hard to understand why anyone would actually palindromically call it "IDDI", but I guess you could.. If you looked at the sign in the Greek alphabety way, you could palindromically call it "IDDI", because the sign is made up of "ΙΔΔI".

• Iota, delta... and yes, very farfetched. – Chowzen Apr 27 '18 at 3:03
• I sincerely thought that someone would guess this quickly, and the "IDDI" clue would be a small reinforcement at best. – Chowzen Apr 27 '18 at 3:06
• I've updated to reflect your "Iota, delta" hint, to be honest I still had to think for 30 minutes straight about how that made sense, but that could just be me not usually having much to do with the Greek alphabet or not being as cluey as I might seem ;) – OnlyF Apr 27 '18 at 7:26
• Also not sure if this is now actually the right answer, but FWIW this sign was the first thing that popped into my mind when I read the question when it was first posted, I didn't post it because I couldn't make a non far fetched palindromic "IDDI" out of it, which seemed a requirement from your comments on the first answers. Only now when seeing the question again with your hints I thought lets just give it a shot, and I posted one of my far fetched "IDDI" explanations. So it was more like the "IDDI" hint ruled answers out, while vague because technically you could call anything anything.. – OnlyF Apr 27 '18 at 7:38

Is it

the double line marking on US roads?
https://en.wikipedia.org/wiki/File:Double-yellow_line.svg

I may be yellow; two-faced I be,


Two lines that may also be white.

But you would be wise to never cross me.


Never cross it or you may encounter vehicles that go in the other direction

I stand straight and tall; my authority's given.


A long straight line. The rule is set in the traffic code.

You'd best follow me if you're want to stay livin'.


Follow it, don't cross it, or you may have a deadly accident.

• Please see my comment on the earlier Answer. – Chowzen Apr 16 '18 at 12:14
• Isn't this just a copy of @TinyTRex72's answer with extra info? – Redwolf Programs Apr 17 '18 at 17:26
• @RedwolfPrograms Well, since TinyTRex72 posted their answer half an hour after mine, I could hardly have copied it. – xhienne Apr 17 '18 at 18:55
• @xhienne oops. I guess they say great minds think alike(ish)... – Redwolf Programs Apr 17 '18 at 21:42

You are a railroad crossing sign, such as the one at https://www.safetycal.com/sites/default/files/styles/product_page_display/public/SG1522.gif?itok=NjQNpDWm:

• So, this is two-faced? and can be called "IddI?" – Chowzen Apr 16 '18 at 12:13
• I guess there are two such signs facing in both directions, so, yes, it is two-faced. The IDDI, however, isn't covered yet. – Alfe Apr 17 '18 at 14:37
• technically, you can call anything iddi. this answer is correct. – omikes Apr 24 '18 at 15:56

Could you be

A wet floor sign?

I may be yellow; two-faced I be,

It is yellow and it says it on both sides.

But you would be wise to never cross me.

You might slip.

I stand straight and tall; my authority's given.

it stands straight up and says "Wet Floor"

You'd best follow me if you're want to stay livin'.

You could seriously hurt yourself if you fall.

Don't
Cross
Me

This might represent the shape?

Regarding the "iddi"

It could mean it is the same in the front and the back?

An almost certainly incorrect partial answer, based mainly on the IDDI hint. You're

Bart Simpson, also known, among other things, as the "I Didn't Do It" kid

I may be yellow; two-faced I be

He's definitely yellow; and two-faced sounds like Bart. Or possibly referring to the different appearance of the character in the early shorts

... and I can't make the rest of it fit.

You are a

yellow traffic light:

I may be yellow; two-faced I be,

Technically amber, buy yellow is often used as the name of the colo(u)r. Generally, a traffic light has a twin in the opposite direction (and often from perpendicular directions, but the opposite one is almost given)

But you would be wise to never cross me.

You should not drive on the yellow light (unless you are not able to stop safely)

I stand straight and tall; my authority's given.

It's the law.

You'd best follow me if you're want to stay livin'.

Don't
Cross
Me

Pay attention to traffic lights...

A number of answers are like signs pointing us in the right direction; a number are not.

Some answers are about static (yellow) traffic signs. These are not incorrect answers, but a traffic light is somewhat different. It's dynamic, and universal.

Here's my guess,

I may be yellow; two-faced I be,

Didi's hair is yellow. Two faced as Didi makes Dexter's life miserable by acting nice and having fun in his lab

But you would be wise to never cross me.

It is wise for Dexter not to piss off his sister.

I stand straight and tall; my authority's given.

Didi is way taller than Dexter and has given authority as she is the first child

You'd best follow me if you're want to stay livin'. Related to first clue.

You better listen to Didi if you want to stay livin'

I guess you could palindromically call me “IDDI”

Didi can be rearranged into palindrome IDDI.

And so IDDI is,

It could be

Donald Trump.

I may be yellow; two-faced I be,

Yellow or orange is often mentioned to describe the color of his hair. Also being envious of other people (which might be attributed to him) is associated with the color yellow.
Lots of people assume him to be a liar which can also be called two-faced.

But you would be wise to never cross me.

He attacks whoever opposes him.

I stand straight and tall; my authority's given.

He is physically rather tall, his authority is now that of the President of the United States, and it was given to him.

You'd best follow me if you're want to stay livin'.

He at least appears to be willing to attack whoever is not going his way, at least in foreign politics.

Don't
Cross
Me

That could be another warning not to go against him, and spelled out in the way he often talks. Monosyllabic.

IDDI

Beats me. For this I didn't find any real clue yet. Some see similarities in him to Idi Amin, but that's a weak trail. Maybe there is an abbreviation I'm not aware of which fits. Or it is because many people think of him as an IDDIot.

• +1 funny (sorry if it was not intentional) – xhienne Apr 17 '18 at 15:32
• No need to apologize ;-) – Alfe Apr 17 '18 at 15:33
• hmmm... "I'm positively yellow with envy?" – Chowzen Apr 18 '18 at 11:32

Perhaps:

A cross walk signal picture is from this wired article

I may be yellow; two-faced I be,

The signal lights are often in yellow containers, and walk/don't walk could be the two faces.

But you would be wise to never cross me.

If you go against the signal you might get run over.

I stand straight and tall; my authority's given.

Usually mounted on a pole and linked to the traffic lights so no reason to doubt the signal.

You'd best follow me if you're want to stay livin'.

Don't Cross Me

Again, crossing in traffic is dangerous.

Could you be:

an Indian cobra?

I may be yellow; two-faced I be

The coloration can be yellow, and the markings on the back of the snake resemble a second face.

But you would be wise never to cross me

Duh.

I stand straight and tall; my authority's a given

A cobra stands erect when confronting a threat. It's pretty clear when it stands tall, it means business.

You'd best follow me if you want to stay livin'

The best way to avoid being bitten by a cobra is to stay behind it.

As for the "IDDI" clue,

This refers to the markings on the ventral side of the cobra's hood that resemble a mirror image of the letters "DI".

I may be

I guess you could palindromically call me “IDDI”

It is a form of ID, hence palindromically it would be iddi.

I may be yellow; two-faced I be,

The badge is sometimes yellow, although it depends on the country. It has 2 faces, the yellow badge (face) and a more detailed id.

But you would be wise to never cross me. I stand straight and tall; my authority's given. You'd best follow me if you're want to stay livin'.

Don't Cross Me

This refers to the owner of the badge, a cop who shouldn't be crossed. A cop has authority and is known to stand straight and tall.

• Isn't that more likely to be "DI-ID" than "ID-DI"? (Depending on rank) – Chronocidal Apr 17 '18 at 10:02

M̴a̴y̴b̴e̴ ̴i̴t̴'̴s̴

It's probably not this, but this is the best I could come up with:

I may be yellow

Warning signs are often yellow.

two-faced I be,

Some signs have images on both sides. Some signs have two alligator's faces.

But you would be wise to never cross me.

Or you may meet an alligator Also presumably some alligators are by streams; and we all know you should never cross the streams (ok, I just wanted to get that line into my answer somehow)

I stand straight and tall;

A sign is straight and tall

my authority's given.

Some signs state the authority who posted & enforce them Also the alligators give their own authority

You'd best follow me if you're want to stay livin'.

If you don't follow the advice on the sign, you may become lunch

I guess you could palindromically call me “IDDI”

OK, time to jump the shark... If I disobeyed the sign, I'd Die?

It is two headed. It is yellow. It is greek.

IDDI is the sounds of the acronym for:

Eλληνικές Ένοπλες Δυνάμεις, Ellinikés Énoples Dynámis)

I'd say:

POLICE LINE: DO NOT CROSS

• Welcome to Puzzling! Can you explain why you think this is the answer to the question? Answers without explanations will be deleted. – Deusovi Apr 16 '18 at 14:23

IDDI

The shape of a drawbridge, where the D's are the moving parts (?) OR The traffic signals around the sign?

I may be yellow; two-faced I be,

The drawbridge sign is yellow, and there's two of them (one at each side) OR The yellow light (?)

But you would be wise to never cross me.

Unwise would describe an attempted crossing of a drawbridge that's up.

I stand straight and tall; my authority's given.

The drawbridge is towering when in the up position (?)

You'd best follow me if you're want to stay livin'.

Obey the drawbridge signal! Your life may depend on it.

Don't Cross Me

Can't cross you! ;-)

Image source/credit:

The double yellow lines on a road

Because:

Follow them, don't go against them, or you'll get in a wreck

• You need to address all of the parts of the riddle, not just a few lines. – Redwolf Programs Apr 17 '18 at 17:23