My suggestion is to simply use Egyptian wall paintings as well as the depictions of the oxhides covering shields.
Mainly you are looking at a reddish brown and cream spots or mottling, sometimes with a very dark, nearly black instead of reddish brown.
Look at Egyptian wall frescoes and it is all there. The more difficult task is to get the right casting. Leaner, rangier and with longer horns than say some medieval bullock.
Also look at the Minoan bull dancer frescoes. Perhaps one of those luscious looking female bull dancers would make make a great command stand or camp for a Minoan army . . .
Would that be worth the burden of all those defensive spear?
I think it might.
