Focus colours within the Czech National Corpus are: black, white, red, blue, green, yellow, grey, brown. (In this order.) They are components of the language centre. From this list we eliminated: deep red, pink, orange and purple.
Our decision is based on our observation of the Czech National Corpus. We must say that language and its users express colours very often vaguely and individually.
But focus colours are the most stable components in it.