In article <59fb53$93d@lace.colorado.edu>, keivom@rintintin.Colorado.EDU says...
[....]
>Also, I'm curious. If there is a green, red or blue wall and I wanted to
>bounce flash off that, could I just stick a filter over the flash that is
>the exact opposite(complimentary?) color.

Yes, but it is darn hard, on short notice, to get the color
just right...;-) Also, in the processing of neutralizing the
color, considerable light would be lost, and with bouncing
flash to a wall or ceiling, there is often little light
to spare...
Hope This Helps