I don’t think that this question if fair on the guys as we men usually have to rely on one colour for our trousers (pants for you Americans) and a different one for our shirts. That’s the way it has to be. Because otherwise you’ll be thrown stones at and ridiculed for ages! Unless it is part of your work uniform, in which case ridiculing will not be followed by stones.
Women can wear the same colour for their outfit and pull it off in style. But I have rarely seen a guy being able to do the same. I certainly would not dare. Anyways, coming back to the answer for the question, if I had to choose one colour it would have to be blue for my shirts and only for my shirts. I tend to favour blue as the colour for my shirts, although currently I only have one shirt that has white & blue stripes (I kind of look like an overweight football player for one of them clubs). But in a crunch I would always look out for blue shirts. It’s the safest bet. As for trousers, everyone knows that I only wear black trousers. It’s been that way since I was a teenager. Unless it’s jeans in which case I have had a beige/light brown pair, blue jeans, gray jeans other than black. But I prefer blue jeans as well. It’s the classic colour.