Dogs are not color blind and they see blue. This site shows what dogs see as they are red/green color blind
http://www.uwsp.edu/psych/dog/LA/DrP4.htm
Dogs hump for other reasons than sexual gratification. It is a dominance motion with them also.
If he was just neutered it may be that he needs a little more time for the hormones to leave his body before he will reduce this behavior.
Hope this helps you!
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