light spectrums - lenses

light spectrums,

they are based on different colour light
red blue ect

can they be changed with a colour lense over a light fixture ?

the color spectrum can be changed by just changing the bulbs on cfl's i know. 6500k for veg and 3000k for flowering.

By using a coloured lens, you would be cutting down on available light, so you would yield worse. Better blast the plant with light, and let it decide what is useable, rather than filtering, and having less light as a result.

This is why both HPS (and also MH) work for both veg and flower stages. The spectrum has some effect, but the amount of light is more critical.