Coboglobin is currently a synthetic protein that performs the same function as hemoglobin. It uses Cobalt in place of the iron atoms.
Blood of this type would be amber yellow in color when in the veins while uncoloured and clear in the arteries.
Quoted from Jim2B on Other blood colors
This the closest thing I can remotely find that's even close to the color of gold. But I recommend giving up on a suitable answer cos it would take a alien creature or some other unknown substances to really make gold blood. Or you could take all that gold from Smaug, melt it and voila.