The other big thing people look over...is you have to make sure you clean them down good, because if it has ever been ArmorAlled then it is basically got grease all over it and the dye will not soak in (same goes for treated leather, I tried dying my original shift boot, but it was treated and failed....so I bought a white leather one).
I used dawn dish soap and a tooth brush at first....then used wax and grease remover after that, because I wanted to make sure it was clean.