controlHighlight

colorControlHighlight documented, in both M3 & GM3:

Light mode: #1f000000 dark mode: #33ffffff.

These are black and white with some alpha. 1F hex = 31 decimal; 31 / 255 = 12% alpha. 33 hex = 51 decimal; 51 / 255 = 20% alpha.

DynamicColors do not support alpha currently, and may not need it for this use case, depending on how MDC resolved alpha for the other cases. Returning black in dark mode, white in light mode.