Board Thread:General Discussion/@comment-90.184.166.27-20140419175031/@comment-27363192-20170413233816

Blood is blue in veins as opposed to red in arteries due to oxygenation from the lungs. When it returns to the heart and lungs it is blue until exposed to the air hence varicose veins that are not a happy thing for older people. The blue veins are what the people in the lab are looking for when they draw blood for test or donations. The Royals have their DNA and the test was likely geared toward that DNA to turn blue.