Folks, I have wasted possibly hours of my free time to put together Yet Another Bloodcolor Chart(TM).
Based on the one from FYAFT (where else?), this chart has been simplified, re-ordered, de-redundantized, etc. It includes a row of possible mutant colors (colors on the other chart that were way too bright for regular blood), which you may utilize or ignore at your leisure, and removes every blood color that would be higher than Feferi. (The color at the end isn’t higher - it’s a lighter shade of the same blood.)
Like it says on the picture (and at FYAFT - peeps know what they’re talking about), if it’s not on there, don’t use it for your fan troll. That includes black, white, any shade of gray, and rainbows.
Also, the big white asterisk highlights a possible non-mutant color for Karkat’s blood, based on his position in the zodiac. I’m aware that it’s cramped and shares a class level with another troll; that’s just the way it turned out.