To start off I'd like to say I understand why we can't dye our entire mount, and our current dye channel isn't complete coverage. It keeps us from being overrun with neon pink bunnies, etc etc.
However, for more customization, could we have a light/dark slider bar for the core coloring of the mount?
Like...for example the springer (bunnyroo) could go from a pale creamy tan on one end of the spectrum to a dark chocolate brown. The skimmer could go from a pale silver to a dark navy color. The sand jackals could transition from pale golden sand all the way to a black sand. On more complex colored mounts, like the griffin it could be a warm/cold color transition slider, from warm brown on one end of the spectrum to cool grey on the other.
This would allow us to have more or less contrast with our chosen dye channel color, while still maintaining visual integrity of the game.