TURBO MODE To convert from HSV to RGB, scratch uses linear models to determine the colors from the hue, then maps it to the RGB colorspace with no view transform. The one I implemented here uses a sinusoidal model to determine the colors from the hue, and then uses a gamma transform to transform to sRGB colorspace (this is because sRGB monitors display light as if it was raised to the power of 2, since we see clear rounding errors in dark colors, but don't in light colors, since our eyes interpret light logarithmically)
Only sinusoidal model applied to hue. And assuming the hue already in gamma space, both saturation and values directly applied to hue. Brightness in Scratch's colorspace is already correct, but hue. Hue plan: https://en.m.wikipedia.org/wiki/File:Hsv-hexagons-to-circles.svg