If you soak the steering box casing in evapo-rust, the markings will show up a lot better. There are varying markings, it's generally recommended to just put back what you find.
The Ford Master Parts Catalog usually lists the color daubs for wheel cylinders. The one in your pic looks like a possible replacement. Originals would be either Bendix of K/H. Guessing this is a rear wheel cylinder?
Would recommend using the Gregory book with caution, there are many errors... the problem with printing reference/restoration material.