Why does blood get darker as it travels through our body

Question

kaylalynnv · Answer

Ive never heard of that one but I do know that your blood starts off blue in your skin (thats why your veins are blue) but as soon as oxygen hits it, it changes red.

aaronq · Answer

Blood is never blue, it's always red. It's a darker red when it's not oxygenated (veins) and a brighter red when oxygenated (arteries). 

It changes from a brighter to darker red because it "drops off" oxygen molecules as it travels through the circulatory system. The actual colour arises from the Iron metal atoms in Hemoglobin (inside red blood cells), it changes colours depending on what it's bonded to.