I stumbled across an excellent tutorial on colour theory which I am sure most readers will find useful.
Simple, Practical Color Theory covers key theories such as Colour Models, Colour Harmonies a section on definitions and Hue, Saturation and Brightness.
Owen James deals with screen colour but at the foundation is good old fashioned colour theory. So if you get terms like tints tones and shades muddled or are not sure what you are doing when push that Saturation slider this tutorial is worth your time. So make a cuppa and pop over to read Simple, Practical Color Theory