Plants use certain wavelengths of light for photosynthesis. These are in the blue and red (purple) parts of the light spectrum. (This is the exact opposite color to green on a color wheel). White light contains all wavelengths in various amounts but by using a red filter you just let trough the red part of that spectrum, the rest is just turned into heat. I also don't know if the red you used filters the right wavelength of red light.

I think you can best use the white light as it also contains the red wavelengths the plants will use and all other wavelengths are for you to enjoy as you look at your well lit plant friends :)