Painting

Today is a painting day.
I've been out with the dogs while Mr M has been to get the paint, then its rollers to the ready.
In fact, we may start upstairs today rather than this room. I went in to blip the new log burner which was finally installed yesterday, only to find that Mr M had already covered it in dust sheets. So that blip opportunity will have to wait.
Question: how many different shades of cream paint are there and how on earth are you supposed to decide?