Omniknight's set icons have random bits of red in them. His cloak is miscolored to be bright red.

Seen on these sets
http://www.dota2.com/store/itemdetails/20066 (cloak)
http://www.dota2.com/store/itemdetails/20067 (bracers)
http://www.dota2.com/store/itemdetails/20036 (cloak)