I'm not sure whether this riddle requires certain knowledge to solve, still I will give it a try.
I guess you are
Copper conductor (copper wire)
You can't see me, yet I'm there
We usually can't see copper wires, since it is either covered with plastic jacket or built inside the concrete wall with jackets.
Under blue or red, white or black
Here comes the vital part: electrical wiring (wiring color code).
We sometimes may found more thinner wires with different colors inside a normal wire. These colors refers to different kinds of cable, such as neutral, ground and different phases from 2-phase/3-phase power. From the link above, blue, red, white and black are applied to wiring by different countries.
For the most obvious example, check Brazil's fixed cable color code.
(OP is from Brazil :D)
I decide if you will live
I can put you to sleep
Copper wire bring electricity to machines, which may capable to decide if someone will live (life support system such as ECMO) or fall asleep (some kind of smart appliances like Nest thermostat?).
I'm with you, as you can see
Whether home, on space or sea
Though copper wire is rarely seen under plastic jacket, we always knew the existence of those electrical wire, whether at home, inside the space station, or under the sea.
There's no use running free
I will drag you back to me
Many people can't live without electricity nowdays, especially a living place without any electrical infrastructure.
Don't try poisoning me, it's pointless
You'll be rendering your life useless
Not sure about this part, poisoning cable sounds unreasonable. Yet, I am sure that those who throw any liquid on it may get a electric shock.
I can harm you, I can kill thee
Yet you crave me and you seek me
I think it is refer to electricity than copper wire itself. Electricity can harm, even kill me, but I need them to post on Puzzling!
"We've been through with each other"
Well, we surely been through about 200+ years.
"It was you who started the fire, I just kept it alive"
Wires doesn't produce electricity itself, they transfer electricity to make sure it won't vanish on the half way to the destination.