Now I realise this seems like an odd question, but does anyone know if there is a file somewhere that lists all the colours used in Minecraft?
If that's a bad explanation, I've linked an image I made showing all the colours used in the "tnt_side" texture. I was wondering if someone had done something similar for the entire game.
Probably the easiest way to do this would be to make a program that examined all the images in a file and compares every pixel to the ones that came before. If the pixel is different, the program adds it to the list, if it matches another pixel from before, it moves on to the next pixel.
I haven't done this because I don't know how to but I'm sure someone does.