I am making an alien race and need help with their biology

[BethSalt]

my blood is gold... rh null

 

[FactChecker]

They like to eat fall leaves to give their vanes that look. They think it looks cool, like tattoos. Currently, the golden-yellow of fall aspen is fashionable.
Don't ask me how I know. ;-)

 

[kered rettop]

I would like a reason why their blood is Cooper/ Rose gold color.
They evolve from a dinosaur bird like creature but in their current timeline they are human looking. One of their most strange characteristic is they got cooper looking veins and their blood is rose-gold color. Which gave the ancient Greeks the idea they were gods. But i would like to have a scientific reason for their blood being that color. thank you.

Some real creatures have a very different colour blood from ours: https://mocomi.com/what-colour-is-blood/
Notice that you only have to tweak the organic molecule a little to get completely different colours. You can be pretty vague as we definitely don't know the whole range of possible molecules.

You can change the metal too. The kid's article above mentions a creature that uses copper. But there must be dozens to choose from - practically any transition metal, for starters: cobalt, chromium, manganese, copper. And maybe uranium or vanadium. It all depends whether you need to stick to the idea of blood as primarily a way of transporting oxygen or tie your own hands by insisting that they evolved from a terrestrial dinosaur.

The further you go away from human biochemistry, the more options you have. And the less likely it is that anyone will be able to contradict you.

You can probably even get a metallic sheen too. Materials like graphite or molybdenum greases can be thinned out with oil to get beautiful streaming effects. And as for colours, you're not limited to what chemistry allows, despite the above. Butterflies - and many other organisms - produce colour through interference effects. The blood cells could do both of these if they were modified a bit. Or maybe the blood contains a different kind of cell altogether. The main thing would be to make it reasonable for such a thing to evolve.