I tried the following:

1. Create HairFromMeshStrips

2. Separate strips into groups

3. Add GroundStrands node

When I do this, every operator after the GroundStrands seems to ignore the groupings I assigned in 2.  (If I don't add a GroundStrands node, the UVs driving the hair colors get messed up in animation.)

This particular mesh has identical UVs for each strip.  Do the strips need to have non-overlapping UVs or something for the grouping information to work?  Would that solve the problem?