Unless he is going to clearcoat them after the chrome coat, don't do that color. All 'almost chrome' powders need clear for longevity, even the ones that are supposedly single stage and dont require it, which is probably what he would be using. If you get any chemicals on them, it will discolor it, even simple green. With a clearcoat, it would be fine, and look like the back side of aluminum foil, but shiny. Kind of like this:
both are the same coating, the quality of the reflectiveness depends on the surface on which it is applied. The caliper is more irregular shaped, so its not as reflective as the timing cover