I took the decals from Wings of Liberty, Heart of the Swarm and Legacy of the Void, then filled them with triangles in TinkerCAD. Thus I now have a fairly close approximation of the decals.
To be mounted with double-sided tape. I recommend blue, purple and gold for Terran, Zerg and Protoss respectively, as these are the default colours of the decals.
The author marked this model as their own original creation.