Is that MSPaint's colour picker? Though I like its basic set up, actually selecting the exact colour I want has always felt a bit awkward. It can be challenging to hit an exact spot at times, and you can't nudge the colour cursor with the keyboard to make up for it, and the Hue/Sat/Lum boxes can't be adjusted with the Up/Down arrows.

My personal favourite is using HSB sliders:

It functions very similarly, except instead of having a 2D hue-saturation grid, it separates everything into sliders, and each slider is coloured according to the current values of the other sliders. Because it's all sliders, I can easily get related colours for my palette by picking an existing colour and adjusting its parameters separately, but without having to edit numbers as I would in MSPaint.
The best part is because it takes up so little space, I can have it as part of my toolbar right above my layers window, I don't have to open a separate colour picker window.

I think RGB, CMYK, etc sliders are rubbish for doing art because they don't tell you anything about the relationships between colours, since they're based on their physical components instead. HSB deals with the three dimensions of colour that are actually relevant to artwork - hue, saturation, and brightness.