clayLabelRingColor function
The colour a clay function label must also reach the label floor on: the inner shade for labels darker than the face, the highlight composite for lighter ones.
Implementation
int clayLabelRingColor(KeyColors k, int edgeShadePermille, int highlight) =>
luminanceArgb(k.label | 0xFF000000) < luminanceArgb(k.face | 0xFF000000)
? clayInnerShade(k.face, edgeShadePermille)
: clayHighlightComposite(k.face, highlight);