Anyone know the answer to this what do the pictures have in common riddle?

[aleczanderjordan]

What do these pics have in common? http://25.media.tumblr.com/887a853519e8ed09ace97573586fe743/tumblr_mhz7s0kkm51s1le89o1_500.jpg

 

[Kaykay]

Cyan

 

[DogStar2]

the color purple or blueish... I'm color blind :-/