In a bar chart I found no way to define if datalabel is inside or outside of the bar. Highcharts computes this depending if the text fits inside or not.

When you have a white background and a colored bar, and you want to have the complementary color for the text depending on inside or outside of bar there is no way to find out which color to set, because highcharts positions the text dynamically. e.g. on changing browser size, the position can swap from and to inside or outside of the bar.

Sample: some labels are inside and some are outside of the bar. Which are inside and outside is dynamically changed by highcharts on browser size change:
https://jsfiddle.net/kc7d6yew/