An implementation of the hue-saturation colour model, which relies on a more advanced metric for luminance. This colour space was developed specially for Grasshopper with the goal of combining the intuitive aspects of hue-saturation models with the axis-independency of luma-chroma models.

The luminance axis of the H*SP colour space is based on the YCbCr(γ) equations, yielding a luminance metric which closely tracks human perception. Hence, the P stands for 'perceived luminance'.

Unlike with other hue-saturation spaces, the H* axis is adjusted by a non-linear squeezing and stretching transformation to increase the respective areas associated with yellow, cyan and magenta hues, which tend to be underrepresented in the HSV and HSL spaces.