Lights that affect color saturation

Sorry if this has been answered elsewhere, I've been looking for a little while with no avail.

Basically, I'm just looking for a starting point here. I'm guessing that it's going to take some shader wizardry to accomplish this, but here's the gist: I want the majority of my scene to look very washed out and be largely globally illuminated. In areas of higher light, I want my colors to be very vibrant, as if color is "bleeding" from the light source. I'm guessing that I can create a shader or image effect that can accomplish this, I'm just not sure how to go about doing it.