I chose to cover the rears with smoked window tint film:
...And the fronts with some 3M reflective vinyl that looks matte black at oblique angles, but reflects bright white when lit from a headlight. This allows it to still function usefully as a reflector. Sourced from ebay, about $20 for a 8x11 sheet.
Reflector off-angle looks black:
Attachment 330817
Reflector on-angle goes silver-white in direct light/sun/flash:
Attachment 330818