ColoRotate

Link:

My colleagues and I developed ColoRotate because, while color is
inherently three-dimensional, all color pickers were flat. From the
feedback we received during beta testing, it seems that those who
engage in computer color selection and design also felt that vacuum.
They found some features of ColoRotate especially appealing, such as
gaining more control over foreground and background colors through
fine-tuning with sliders, and easily creating meaningful palettes.