ahh yeah it's the tipical slightly-different-but-looking-the-same colors haha but really it's 18 colors, although i didn't really bothered having a reduced pallete or sth x)
Nice! Very clean and great AA. One thing, though: you've written 18 colours but you have 21! 
Fair enough; if you don't have a program to identify which pixels are off then it would be a major operation to find. I don't think anyone is going to get upset over 3 stray colours.