You are:

Deja vu

Rather than usual I'll have grey area,
other times I don't.

Typically you know you're having a false memory (not a grey area), but other times you may strongly be attempting to recall why it's familiar or if it is real (grey area).

You could say I'm being feared by,
gladly only to a few.

Usually deja vu is benign, but sometimes it's an inauspicious or feared remembrance of something bad (e.g. uh oh, this doesn't feel right).

Being part of me, are you?
I don't really care.

Deja vu, in a sense, is a joining of two times. You don't care because you're a false memory and it's all in my head anyway.

Vision or imaginary?
Only your mind knows.

The perplexing nature of deja vu leaves it to our mind to determine if this memory is true or false.

Title: I never made you blinded, or am I not?

Did the deja vu mislead me or are does the memory "not" exist?

You are:

Deja vu

Rather than usual I'll have grey area,
other times I don't.

Typically you know you're having a false memory (not a grey area), but other times you may strongly be attempting to recall why it's familiar or if it is real (grey area).

You could say I'm being feared by,
gladly only to a few.

Usually deja vu is benign, but sometimes it's an inauspicious or feared remembrance of something bad (e.g. uh oh, this doesn't feel right).

Being part of me, are you?
I don't really care.

Deja vu, in a sense, is a joining of two times. You don't care because you're a false memory and it's all in my head anyway.

Vision or imaginary?
Only your mind knows.

The perplexing nature of deja vu leaves it to our mind to determine if this memory is true or false.

Title: I never made you blinded, or am I not?

Did the deja vu mislead me or does the memory "not" exist?