I have searched one more time... and this time I have found RE document about Xctrl protocol (the way X-Touch communicates with X-Air). And colors are mentioned.
As the next step I have to check that Sonar really export color (I mean check that API is working on Sonar side).
If that is the case, than it is theoretically possible to get colors on X-Touch from Sonar (with a limitation in colors, X-Touch support limited set of colors, so it can display only "nearest possible" to actual Sonar strip color).
Practical part does not look as good:
a) I will have to find time. It can happened that sending colors is not compatible with Mackie mode, in this case the whole communication should be replaces. In the documentation, color information is sent with text content, which in turn is sent not as for Mackie. So display operations should be replaces in any case.
b) I do not think I am ready to work remotely with that, too many unknown variables and the documentation is not official. I do not have the device and I have no plans to buy one myself. So community will have to sponsor one X-Touch. Probably that is also a good way to check some people really want that happened