Red flash yo

Got THIS BOOK for christmas and have been slowly working my way through it when I go to bed in time to read :P
There is a page about super-contrast, where by the photographer and author shoots a portrait infront of a green wall (out of range of the flash) and with a "red-gel" over his flashgun. I had none of this ....red gel... so i just wrapped some red electrical tape round it, just as effective. Can't wait to take more with my blue and green tape ;)