Ask A Scientist© Biology Archive

 
Question:  A sixth grade class wants to know if, in the human body, blood is ever blue.
Reskin School, Glendale Heights, IL

Answer 1:  Sure, close to it.  It's a very dark bluish red in the veins.  Just look 
at your arm veins.  --ProfBill

Answer 2:  Generally blood is red or dark red.  It appears bluish through our skin, 
so that's why our veins appear blue.  Once blood has exchanged its oxygen for carbon 
dioxide,  it gets a little darker, but not really blue.  There are some interesting 
genetic studies on a group of people having blue pigment in their skin, though...
Ellen Mayo