Black absorbs light - the less you can make out the surface of the material, the more absorbtion is taking place. Put on your best suit, and roll about in a big pile of photocopier toner powder - that is black!! Since infra-red has the same qualities as any other light it will reflect best from a highly reflective surface, e.g. a mirror. Make a suit out of that mountain rescue 'space blanket' material! (I think some special forces use this basic idea to help escape infra-red detection).