why does blue blood exist in our heart?

[valencialiew]

until my daughter was born, we just realise our body have blue blood and not only red blood. Doctor told us blood blue more than red blood in our heart will cause dangerous to heart and body. how is the blood form?

[JackBean]

maybe because it is never blue

[Adz795]

Blue blood = deoxygenated or oxygen deficient blood.
Red blood = oxygenated or oxygen rich blood.

More blue blood means less oxygen supply to the body.

[JackBean]

except that the deoxygenated blood is not blue, but dark red

[JackBean]

there was this noce topic about color of blood about763-48.html
I hope this topic won't last for five years as well...

[Adz795]

Well, yeah but with "blue" blood valencialiew meant deoxygenated blood. That's the convention.

[michimichi]

blue blood is not literally blue in color...