I've never quite understood as to how people choose their favourites of... anything, not just colours. There are just so many options to choose from that in my mind I like relatively equally. I used to have an ideas on what my favourite colour was, but over the years it's changed because of how much me and my characters have developed.
Nonetheless, I know for a fact that it's either green, red or silver. The last of which is sort of an expanded upon grey because grey is too boring and dull, though it's usually associated with me.