I do not know if this will help anyone, but you might try doing a "reset to defaults" on the data labels and then go through setting up again. What I have found is that if a conditional formatting for value color is chosen and set, and then a field gets added(say to the Y Axis to show differing categories like yes/no above), then new edits to the datalabel color will not take effect because a previous setting is still there it would seem(artifact setting?).
I found this while trying to make a simple example of an issue I am still having with datalabels conditional formatting of color using a measure value. This however did not fix my issue particular issue, but I thought at first I had replicated my bug of where it was having different text color value than the actual measure value.