At the moment I use the template Purplemine (https://github.com/mrliptontea/PurpleMine2), because at least in the CSS file it offers the possibility to provide the trackers with different colored labels. This is particularly helpful in the Gant diagram to keep track of things. The colors are also used to highlight the respective IDs in the issue overview.
It would be even better if I could specify the colors directly in the definition of the tracker (Administration-> Tracker) myself