It was too 6-6-500, then I've decided to 1009 it with more color, but it became too 54-1-500.
What could be it?
If we convert the numbers to Roman numerals, we get that 6-6-500 is "VIVID", 1009 is "MIX" and 54-1-500 is "LIVID". So the first sentence becomes
"It was too vivid, then I've decided to mix it with more color, but it became too livid."
I think it is
based on the partial answer
red is a color which is vivid, then I mix it with blue to get a livid color, which is purple