The selected color box above the controls will change to the new color. The little square to the left in the color map display will change too. And, most importantly in many cases, the fractal in the active drawing window will change too. While all the colors can be thought of as red, green, blue combinations, sometimes it is more convenient to think of colors as conisiting of a hue, saturation and brightness. Hue corresponds to the frequency of normal light, the position in the rainbow you might say.
Saturation is a measure of how much of the color is there, as opposed to just being a shade of grey.
Values range from 0 for grey to 100 for full strength color. Values range from 0 to 100 here to. The little button in the lower right hand corner of the color map editor window allows you to switch what the sliders and the number boxes to their right represent. Try clicking it. If the sliters are set to RGB you can still enter HSB values in the bottom boxes.