It seems that since World War I at least, most of the world's militaries' combat uniforms are designed to be somewhat difficult to notice, usually a drab grey, green or brown from what I can see. Modern combat uniforms take it further by using patterns designed specifically for camouflage.
Meanwhile all the "medieval" uniforms I see tend to be colourful things meant to display their countries' colours and such.
When did things change? How did we get to the patterned camouflage uniforms we use today?
EDIT: I'm mainly curious about Europe, although the Middle East and Asia would be of interest as well.
I would suggest specifying which area of the world you are asking about, especially considering your example pictures are of peoples with very different history.
I'd also suggest you somewhat specify the time period, because although you are asking a question of when I can tell you that camouflage had been used in some sense since before the common era.
