Most insect "blood" is colorless, but some insects do have red compounds in their blood. Some natural red dyes are made from bug blood.
>>25276967What makes most vertebrate blood red is the iron in hemoglobin molecules (how we transport oxygen through out blood). If a species use a different molecule, like hemocyanin (with copper instead if iron), their blood may appear a different color (it would be blue in that case). Horseshoe crabs use hemocyanin. There are more, I'm sure.
