other than a black metallic, or some charcoal colour , are all Black paint codes really just the same , Black is Black is Black ?

 

Yep, pretty much.

I have a can of D403 (BASF's "OEM Black") which I use for 99.9% of all OEM black shades.

If you mix the actual paint codes, most will include a dash of white, a dash of blue, but even mixing the formula will get you a colour that is indistinguishable from the can of straight D403.

If it doesn't match the D403, its generally not black