Alien Blood: Played straight, in many varieties.  For example, eldrae blood is close to indigo in color, due to the not-hemoglobin it uses (borrowed from Elieran bluelife, which is indeed mostly blue; and it would lead to noticeably different skin tones if they weren’t all so damn pale anyway).  Kaeth blood is silvery-white, and notably conductive.  Myneni “blood”, really crystalplasm, is whitish and feels sandy.  Esseli blood is red-orange, and mirilasté blood is a fluorescent magenta.