Drag sliders to change hue, saturation, lightness (HSL) and ghost. Or drag the RGB sliders to show corresponding HSL. >> More info: http://en.wikipedia.org/wiki/HSV_color_space << The values for Hue and Lightness correspond to those supplied to the built-in 'set pen color' and (almost) 'set pen shade' blocks. The "set/change pen saturation" & "set/change pen AHSL/ARGB" allow extra pen control (not provided by the built-in pen blocks). When using these blocks, you also need to replace the built-in "set/change pen color/shade" with the supporting blocks. Note that the blocks 'know' about each other, so you can set a pen colour via ARGB, and the pen's known HSL values will be updated so you can use the other change blocks from that new colour. SEE comments INSIDE for more info and examples. Note that the shade is very slightly different to the built-in shade, with zero producing absolute black (unlike the built-in pen block). Please scatter liberally and at will throughout your own projects :) (Though it'd be nice if Scratch had saturation built-in... please...?)