Google >make black rubber roof white

Here is a link that might be useful: Paint it White

mxyplx, that looks like exactly what I need. Thanks.

The membrane is probably synthetic rubber known as EPDM. There are thousands of coatings available so it is important to use what the manufacturer recommends and to be sure is has not aged too much for good adhesion.

Coating it will make repairs and seam checking more difficult and expensive so you should repair it well first.

The coating is unlikely to reduce the temperature inside the dwelling much unless there is no insulation in the roof and you are in a very hot sunny climate like south Florida.

The best approach is to wait until the roofing needs replacing and install a white EPDM membrane.