Why Are Veins Blue While Blood Is Red?

According to SAEDNEWS, quoting Soraya:

Based on a report by Science Alert, human blood is red because of the protein hemoglobin. This protein contains a red-colored compound called “heme,” which is very important for carrying oxygen through the bloodstream.

“Heme” contains an iron atom that binds to oxygen. This molecule transfers oxygen from the lungs to other parts of the body.

Chemicals create specific colors in the eye based on the wavelength of light they reflect. Therefore, oxygen-bound hemoglobin absorbs blue-green light and reflects red-orange light, making blood appear red.

Sometimes blood may appear blue through the skin, and you may have heard that the blood inside our veins is blue, but this is a misconception and human blood is never blue.

The blue color of veins is only an optical illusion. Blue light has a short wavelength (approximately 475 nanometers) and is scattered or distorted more easily than red light. Because it scatters easily, it does not penetrate deeply into the skin and may not even reach a depth of one millimeter. When blue light hits the skin, most of it is deflected. If you shine blue light on your skin, what you basically see is blue skin, and it becomes difficult to detect veins. You may have noticed that blue lighting is used in places such as public restrooms to prevent intravenous drug injection.

Red light has a long wavelength, meaning it is less likely to be distorted by materials and can move and penetrate more easily. Red light can penetrate well into the skin and body tissues and reach 5 to 10 millimeters beneath the skin, where many veins are located. When red light reaches the veins, hemoglobin absorbs it. If you shine red light on your arm, you will see some reflected red light along with dark lines where the veins are located. This phenomenon helps medical personnel draw blood by shining red and sometimes infrared light onto the arm.