KarenClark has it.
Pigments [reflective] subtract light by selective absorbance.
Light [radiative] is additive.
Think of the display you're looking at right now.
White's RGB [red/green/blue] value is FF/FF/FF [hex] or 256/256/256 decimal.
256 is the maximum value for displays.
Guess what the the RGB value for black is ... 000000.
That would qualify as absence of color if that term even has meaning.
Black is absence of LIGHT.
Absence of COLOR is more meaningfully defined as NEUTRALITY of color - equal amounts of RGB on a display produce shades of [colorless] grey.
However, PinWizard could still argue that one of the wires is BLACK so his answer of 24 could still be justified.
Except, one could argue that BOTH black and white are neutral, therefore colorless, then the number would be 6
Except for the fact that the OP says ...
Sorry PW, you've given away the claim of 4 colored wires in the answer
if you specify 5 colored wires in the puzzle.
Creative, tho... points for that.