Noun
English Wikipedia has an article on:respiratory pigmentWikipedia
respiratory pigment (plural respiratory pigments)
(biochemistry) any of several coloured metal-containing protein pigments which combine reversibly with oxygen and which are found in the tissues of vertebrates and invertebrates and whose role is to transport oxygen
It is thought that tunicates (sea squirts) might use vanabins (proteins containing vanadium ) for respiratory pigment (bright-green, blue, or orange). Source: Internet
There is no true heart and the blood often lacks any respiratory pigment. Source: Internet