• Question: Is our blood actually yellow? If it is, why?

    Asked by maggie246 to Ed, Katie, Sam, Steve, Vera on 21 Jun 2011.
    • Photo: Ed Morrison

      Ed Morrison answered on 20 Jun 2011:

      Blood cells are red when they have oxygen in them, and blue when they don’t. If you separate blood in a centrifuge, you get two bits – the blood cells and the plasma, which is the rest. The plasma is yellowy because of the dissolved bits in it, I’m not sure exactly what. There’s no particular reason for it being yellow, it’s just the average colour of the stuff floating in it.

    • Photo: Vera Weisbecker

      Vera Weisbecker answered on 20 Jun 2011:

      Just what Ed said.

    • Photo: Katie Marriott

      Katie Marriott answered on 20 Jun 2011:

      I agree with Ed. Plasma is a yellow colour but our blood looks red because of the blood cells are carrying oxygen. Blood looks blue when they are not carrying oxygen but we never see this because when we have a cut the blood is exposed to air so it looks red.

    • Photo: Sam Tazzyman

      Sam Tazzyman answered on 21 Jun 2011:

      I never knew plasma was yellow – thanks Ed.

    • Photo: Steven Daly

      Steven Daly answered on 21 Jun 2011:

      I think that blood without oxygen is actually just a darker shade of red. Veins look blue due to pigments in them I think, rather than the colour of the blood. If you have ever seen someone giving blood, that is done from a vein and it is a dark shade of red.

      As Ed said, the plasma is yellow because of the things disolved in it, it is mostly water.

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