Shields change color when in head slot (For entities with the capabilities)

When you replaceitem a shield into the head of any entity that can have the shield in its head slot, it changes colors:

(Tested on Skeletons and Zombies, but should work on others)

/replaceitem entity @e[type=Skeleton,r=5] slot.armor.head minecraft:shield
/replaceitem entity @e[type=Zombie,r=5] slot.armor.head minecraft:shield

Video/gif:
1 (Zombie Only): http://gfycat.com/LeadingSoupyAkitainu
2 (Zombie and Skeleton): http://gfycat.com/MiserableFarEwe