Reflexite seems to be the brightest reflective tape on the market. There are several versions.
V98 - more conformable for complex curves, stretches, can be repositioned, adhesive increases in strength over time
V92 - thicker, stiffer, less conformable, will not stretch, very strong adhesive
http://www.findtape.com/ was the cheapest source I found.
It seems that all of 3M's black tapes reflect white. No other reflection colors are available.
"3M Scotchlite Reflective Graphic Film 580-85 E Black" removable with heat, max durability 8 years, 200um thick
"3M Scotchlite Reflective Graphic Film 680-85 Black" permanent, max durability 9 years, "premium performance level", 180um thick