Only on the andrewsarchus ones. You dye it when not equipped, like a normal saddle, and paint on it while the andrew wears it (and you can take the saddle off and put it back on, the drawing stays. I guess because it's somehow technically on the andrewsarchus). Andrews even have an option to switch between the tower part of the saddle and the armor part of it (for that hold the interaction button while looking at the andrew, go into its options and toggle painting target one)!