What color is the blood in the human body?

In different blood vessels, blood has two colors: bright red and purplish red because of the different amount of oxygen it contains. After breathing enough oxygen into the lungs, the blood is bright red. After this blood sends oxygen to all parts of the body, the oxygen decreases and the color turns purple. This purple blood turns blue through the skin and blood vessel walls on hands and feet. Bright red blood containing a lot of oxygen is in the deep blood vessels of the skin, which is invisible outside. There is also a saying that when you look at things through a piece of colored cellophane, the color of things will become different from the original color. Similarly, the blood vessels we can see from the skin are veins, and the blood flowing in the veins is dark red. This dark red is covered with a layer of yellow skin, so it looks turquoise. Although blood is red, blood vessels and blood are different. The blood vessels look green. How can I put it? For example, if you take a yellow hose and tap water, you will say: Ah? Tap water is obviously colorless! Why does the water pipe look yellow? In fact, yellow is the color of the water pipe, which has nothing to do with the solution in the root. Just like our blood vessels, although they are full of red blood, blood vessels are composed of endothelial cells and some connective tissues, and of course they have their own colors.