Not sure I understand your question but I'll take a shot at it
I think it means the same thing as looking at what you're wearing before you go out of the house in the morning.
Kind of a plaid shirt/checked pants thing.
If the piece allows you the freedom of choice for the colors you'll use, you want to figure out what you want first.
And think about whether the colors would look right on the subject as well as if they go together on the piece.
I did the old Fort Duquesne El Cid bust several years ago and had a very tough time picking the right colors to use.
One on line friend helped me out by taking my in progress shot and applying several different color combinations with software.
I'd suggest you try to find other painters versions on line to help you decide.
Also, if it's an historical subject, look for paintings or photos of the subject to help with ideas.
Hope this helps.
Craig