When it comes to blood, the color red is not just one hue. In fact, there are many different shades of red that can be seen in human blood. The reason for this is due to the presence of oxygen in the blood. When blood is exposed to oxygen, it turns a bright red color. However, if there is less oxygen present, the blood will appear to be a darker shade of red. Additionally, factors like dehydration and certain medical conditions can also affect the color of someone's blood.