Are you thinking competition tack (what dicipline) or just for plain old riding??
Hunter Jumpers is what will be the main discipline with him tho with his movement, dressage is going to for sure be a consideration.
I like dark havana or red havana leather on black horses. Both are also acceptable in Dressage. I have a red havana Dressage saddle and I got a lot of compliments on it from judges . Robert Dover was pictured on the cover of the USDF journal a couple of years ago in brown tack. Brown USED to be the preferred color for Dressage, back in the 70s and 80s. Black as seen as "cheap". It came in to favor in the late 80s and early 90s.