EmeraldW, it depends on what you need, more of the specific light colour or blocking out of other colors. A filter will do absolutely nothing to increase the level of red or blue light provided from any source, but it will block the other one's as BrownOut stated, the question being is it these other colors of light that are bad for the plant or that the specific blue/red you're looking for is better for the plant? That needs to be clarified or there's no way to suggest what's best. Brownout's more than right about the spectrum of LED's they're VERY narrow, so narrow in fact you need to specify the specific range your plants like or you may chose the wrong LED's.
Flourescent bulbs are relatively 'peaky' in their spectrum, could be outside of the range you need, if this if for plant growth then you'd generally use 'grow lights' which is nothing more than a specialized phosphor blend to produce the broadest range of spectrum, the plant takes what it needs, though again this is different if there are specific parts of the spectrum that cause damage to the plant that you're trying to avoid. If it's UV specifically that you're trying to avoid there are sprays you can get that will go over any plastic/glass surface that block UV.
If all you're trying to do is block the UV then a UV blocker is all you need, again a filter will do NOTHING to produce more of a particular spectrum of light, in fact even the best filters will still block at least some of the desired spectrum.