Hue, Saturation, and some third thing

Besides RGB, other common color values used in art software are Hue, Saturation, and Brightness (aka Value/Lightness). Unlike RGB, it separates the color spectrum from the white, black and gray tones. It can be helpful to have both RGB and HSB sliders to work with. Personally I find RGB more useful for color balance and finding interesting color combinations, and HSB for fine-tuning color shades and looking up color compliments.

Hue: represents the color wheel, with values from 0 to 360 degrees. Red, green and blue are 120 degrees apart, and so are yellow, cyan and magenta.

Saturation: represents the blend of the hue and brightness values, like mixing red and white paint to make shades of pink. Just red and no white would be 100% saturation, and just white and no red would be 0% saturation.

Brightness: represents the range from white to black. 100% bright is just white, 0% bright is just black, and all values in between are shades of gray.