I will admit my factual knowledge in this area is scant at best and I find the use of military style camouflage somewhat unsporting. This is only a personal and again I'll admit a prejudiced view on my part.

The only scientific study that I have seen and found believable was that some ruminants can see colours to some extent. I beleive deer hunters, particularly in the USA have studied and generated much discussion on camouflage probably as much or more as the military forces. I find it hard to seperate myth from marketing from fact.

I won't go into the other principles of concealment such as shape, movement etc., All I can go on is my own observations, and in thick bush as far as colours are concerned, grey or blue is hardest for me to see.