Why would veins look green?

Answer 1

That was a pretty deep bruise that is now mostly healed. All bruise colors are from hemoglobin, the red compound in red blood cells. This causes the initial red/purple color of a new bruise. As the hemoglobin breaks down it turns into biliverdin, which causes the greenish color. That will break down into bilirubin which looks yellow. Then the breakdown will be completed and the bruise will be healed.

Answer 2

A bruise occurs from blood leaking from damaged skin tissue into the interstitial layers of the skin usually from an impact. It will be dark from the onset but will lighten to a greenish-yellow color as the body cleans these dead blood cells out of the damaged area. It will eventually clear up all the way.

Answer 3

A bruise that is green was fairly deep but is almost healed. The bruise color comes from blood trapped in the tissues. It changes color as it is broken down and removed by the body. The blue/black color that it starts with is the color of blood with no oxygen in it. It fades through several colors ending with pale yellow. The green says there are very few red blood cells left at the bruise site. Soon it will be yellow and then gone forever. ;)