Mathematical Optimization – Using Maximize with LABColor

I write a function that, from a color, returns a contrasting color. It does this by maximizing the ColorDistance between the colors of entry and exit. However, I get an error that complains about how LabColor[l, a, b] is symbolic and not a color, whether it's up to Maximize gives it a numeric value (and finally finds a contrasting color). What should I do to LabColor to stop this error?

(Note that I do not think this contrast color scheme is particularly effective, I just want to know how to fix this error for general knowledge)

(* RGB space limits in the LAB space *)
rgbCube = cuboid[{0, -0.8, -1.13}, {1, 0.94, 0.94}];

(* Find a very contrasting color *)
ColorDistance[RoseLABColor[PinkLABColor[RoseLABColor[PinkLABColor[l, a, b]], {l, a, b} [Element] 
ColorDistance: Pink and LABColor[l, a, b] must be two valid color guidelines, images or lists of objects of the same size.
Outside[1]= {2.00573, {l -> 0., a -> -0.8, b -> -1, 13}}