About & How to use
I have seen quite a few online colour pickers. But few of them were as full-featured as Sharp Color Picker. It has an easy-to-use panel for just point and click for your standard 16.7 million colours. It supports 140 colour names and 216 browser-safe colours for a wide range of easy-to-pick colours. For more advanced users, it has controls for fine tweaking any colours created.
Red, Green and Blue
Red, Green and Blue are called the additive primary colours, that is, those used when mixing light. The possible values range from 0 to 255. The hex value typically used in HTML/CSS works the same way, except it works on a based 16 counting system represented by 0 to F. So the first two characters (not counting #) are how much red is used, and the next two are green, and the last two blue.
Hue, Saturation and Brightness
Many people favour the HSV or HSB system of representing colour because it is much closer to how humans think of colour. What colour? How much? and how dark? It is much easier to guess what the colour will be before checking, and hence easier to find the one you want. That is why the actual colour-picking devices use this method, not red, green and blue controls.
The colour scheme control uses a straightforward colour wheel to help select related colours from the current one.
Browser Safe Colors
Many years ago, designers had to be careful that the colours they chose would work on 256 colour systems. Of these, 216 were consistent between Windows and Mac because the same math formula generated them, the other 40 being picked out to bring to total to 256 – a nice number in the world of binary. Though it is almost a non-issue now, I still use them in the palette because they give an evenly spaced set of colours that can serve as a starting point for finding the colour you want.