One is by far the ugliest number when it comes to working with color. A lot of people find it easier to work with HSV values as opposed to RGB values, mostly because it's much more intuitive. I don't blame them, I use mostly HSV myself. However, there are a few pitfalls that come with that territory. So when working with HSV make sure to check your RGB values for these issues.

Let's start by taking a basic image with 3 spheres The top left is pure red RGB(1,0,0), top right green RGB(0,1,0) and bottom blue RGB(0,0,1) as well as a plane underneath with a gray material RGB(0.5,0.5,0.5), for showing the light color. Keep in mind that this is a very drastic situation. As this entry will hopefully teach you, you almost never want RGB values of either 0 or 1.
For this first image we have a white light for a starting point.

If we look at the RGB values for this white light we have (1,1,1) which is good because they're not zero. Now lets try a different scenario.

This image has a pure yellow light in it with RGB(1,1,0)

Now it may seem obvious not to use a light of this color because there is a value of 0 for blue. But this same color in the HSV scale looks deceiving. The saturation in the HSV scale for this color is 1. No zeros, so there should be no issues you may think. However, a saturation of 1 means one or two RGB values equal 0. In the case depicted above this blue is that zero.

So maybe the problem lies in the materials. If we desaturated the materials there shouldn't be a problem....

This is what happens with a purely yellow light when its intensity is extremely high. Why doesn't it resolve to white?

Well, one must ask themselves what colors are required to make white, and they are red, green and blue. No matter how bright this light gets even with a white material on the sphere there will not be any blue present to create white.

The solution? Stay away from saturation values of 1! My recommendations for HSV are to keep the Saturation values below 0.8 and keep the Value between the range of 0.2 and 0.8. As for RGB 0.2 - 0.8 is a good range. Of course there are always exceptions to the rule but this is good for a general guideline.

Finally here are renders with saturation reduced from 1 to 0.8.