I just tested this in X3e, it works there too.
1. Click on the track number in the Track View's header for the track. The field behind the number turns bright blue.
2. Ctrl-click the track number in another track.
3. Repeat step 3 for all the tracks whose color you want to change.
4. While holding down the Ctrl key, click on the little color chooser strip for one of the tracks.
5. When the color pop-up appears, you should be able to hover over colors and see the colors change for all selected tracks.