Wait. I knew it was one 20w LED, but a white one? That makes no sense at all. LEDs don't emit the full range of visible light. This is why when you have RGB all on, it is not a true 'white' because they don't cover the range to make white.
Color media, be it gel or glass, work by blocking certain parts of the visible light spectrum to make color. So we have a source that doesn't emit the full range of visible light with color media to try and change it different colors? Even if they were specially made for LEDs and corrected for that, the amount of light lost from a smaller part of the spectrum would make colors pretty much useless.
LEDs get their strength from being color additive, not subtractive like conventional lights. The reason why it works well in conventional lights is because you are starting with a powerful source to begin with. The whole concept is completely backwards I am sorry to say.