We're probably stuck with those choices. I've written Word macros to set highlight colour via code like this:


Selection.Range.HighlightColorIndex = wdNoHightlight


After the equal sign, you can substitute values such as...



wdYellow
wdTurquoise
wdBrightGreen
wdGray25

There are 20 available colours. If there's a way to create custom highlight colours, that's way beyond my skill set! I doubt it can be done.



I don't know Outlook VBA nearly as well as Word VBA, but it's hard to imagine this would be different in Outlook.