standards - Correct formula for determining the hue of a CIE L*a*b* color - Stack Overflow
EasyRGB gives the following formula for determining the hue (and chroma) of a CIE L*a*b* color: var_H = arc_tangent( CIE-b*, CIE-a* ) //Quadrant by signs if ( var_H > 0 ) var ......