If "people in power wear grey, the colour of steel" then how do you explain why actually the MAJORITY of people wear grey?

The majority of people are not in power. The majority of people wear grey.

The fact many leaders also wear grey in my view is a sign of conformity and a lack of aesthetic vision. Which is fine if you're not into wearing colour.

You know my reading of the grey trend? Most world leaders are old men. Most old men don't feel confident wearing colour because they are aged and wrinkled and society says that older people don't look good wearing colour. I also think it's because most powerful people are men, and men are taught by a homophobic society, that colour is feminine and feminine = weak (which is not TRUE it's just a conservative and sexist perception). So they are afraid to wear colour unless it's blue. Whereas powerful women actually can get away with wearing colour because people expect women to like colour. So Hillary Clinton can wear jewel toned pantsuits, and so can Angela Merkel, without the backlash that a man who wanted to wear let's say, yellow or bright red, would get (even though a couple of hundred years ago the most powerful men in the world were also the most colourful). So even if men wanted to wear bright colours, they usually cannot without being considered gay and sadly society still views gay as being weak. Which it obviously isn't. The exception to this is African nations and Pacific Island nations that have never had a stigma against men wearing colour. So it's not that people from these cultures wear colour BECAUSE they're oppressed, it's more that they haven't had their inclination to wear colour steamrolled out of them by the influence of Western culture.

The only colour that doesn't have the association with femininity at the moment is blue. Lots of world leaders wear blue. In fact that picture of Mao wasn't wearing grey he was wearing blue.