Now that slimefolk, with their technicolor flesh, have been introduced into play, it stretches the suspension of disbelief to have all slimes bleed the same light cyan color, when logically, the spilt slurry should be, unless otherwise dictated by the player of the slime, the color of the slime's material. This could be solved by setting the slime blood color equal to the body color, but I'd like a more universal solution, because it's not only for slimes I'd like to deviate from the set species blood color for.
I, for example, play a number of non-akula fish, namely Ophelie Sauveterre and Ainslie Grzeskiewicz, a space carp and eel respectively, and in the future, hopefully many more. Being forced into having blue blood forces me to shoehorn in explanations for why someone who should have red blood has blue blood instead.
Other characters, like the xenomorph-hybrids I see around, could profit from being able to have green blood. Bug-people could profit from being able to have yellow or white blood. The non-akula sharks (and other fish) might like to not be bound to blue blood. The faux-demonfolk could take advantage of black blood or any other color their kind could have.
This change would simultaneously lift unrealistic restrictions to a certain blood color as well as allow for a greater degree of exploration with character design. The only consequences I can see are people ignoring the proper blood color of a lore-handled species out of ignorance or with an unsatisfactory explanation as for why their blood color deviates. The ideal form it would take is a setting underneath body color in char setup.