Ok, I put the individual ways into the parent relations and kept the subrelations for the three individual sections.

frankly, I still think this is https://wiki.openstreetmap.org/wiki/Tagging_for_the_renderer

and xctrails (and also openstreetmap.org) should be fixed to support superrelations. There is a segment that the purple and red section share, so colour cannot be applied correctly to that way. The main change was actually breaking the purple way into its constituents accroding to the schematic map on-site (picture is linked above) plus aligning everything in the area to a more proper spot.