Conclusion Your blood’s color tells a story about what’s happening inside your body. Normal, healthy blood ranges from bright scarlet to deep crimson, depending on its oxygen content.

Across the tree of life we can find blue blood, green blood, purple blood, even clear blood. Why does it come in so many colors? Of all the juices in your body, blood is by far the most important.

In a groundbreaking development, French scientists have identified the world’s rarest blood group, known as Gwada-negative.

Not to B-negative, but your blood type could offer a clue to your risk of having a stroke before 60. “The number of people with early strokes is rising,” said Dr. Steven J. Kittner, co ...