For HSV, where does the angle start form? Is 0 degrees red? Are green and blue located at 120 and 240 degrees?
@HelloWorld The coordinate system is chosen arbitrarily (but consistently); what you describe sounds about right. You can find a detailed description here.
An interesting thing to note is that the color "shape" of Lab is non convex and so a naive linear interpolation can produce a color that is actually outside of the color space.