I apologize, I read the original question wrong. I thought you were meaning how many "different" colors are there in early mustangs?.
All that book will do is give you the the differnt colors used and the production totals for stuff like: Hardtop, Standard interior; Hardtop, Deluxe interior; Convertible, Standard interior; etc... as well as the paint codes for the color you want from Ditzler, DuPont, and Ford.
Just came across your long ago post on the production numbers for '65 Stangs in Prairie Bronze. I have a 65 Convertible in Prairie Bronze with Palomino interior. I will try and find my source document but someone did some calculatioms against some Ford numbers and a few other sources and made an estimate of 2, 924 painted Bronze in 1965. Total production was over 500,000 so a pretty rare color. Mine also has the Ford Factory option for the Spotlight. I'd love to know how many Mustangs have the factory spotlight...