What color is your blood in deep water?

Yes, human blood is green in the deep ocean. Objects don't really have an intrinsic color. Rather, the color of an object is determined by three factors: 1) the color content of the incident light that is illuminating the object; 2) the way the object reflects, absorbs, and transmits the incident colors of light; and 3) the way in which the detector such as your eye or a camera detects and interprets the colors of light coming from the object.

Blood mostly reflects red light. Interestingly, though, blood also reflects a little bit of green light. If we shine white light (which contains all colors) onto the blood, blood looks red since it reflects so much more red light than green light. However, if we use a light source that contains all of the visible colors except red and shine it onto the blood, the blood will be green. With no red light present in the first place, the blood can't reflect any red light. The only thing left that it can reflect is the green light. The blood is therefore green.

The blood is literally green. In fact, human blood is always a little bit green. We usally don't notice the green color of blood because there is typically so much more red light being reflected by the blood. But if you shine a light on the blood that contains green light but no red light, the green color of blood becomes obvious.This is exactly what happens deep in the ocean.