While there are lots of ways to change color content of a Grasshopper definition, here is a script that will color code groups for Rhino.Inside.Revit for common identification of components in Revit:
GroupColor-Selected.gh (23.2 KB)
Based on the color specification here: https://dynamobim.org/dynamo-graphic-standards-at-white-arkitekter-ab/
Thank you to @timonielsen for the original Grasshopper script this is based on here: http://blog.rhino3d.com/2019/11/color-coding-groups-fast-in-grasshopper.html
And @eirannejad tweaked it a little by adding the
Selected Only toggle.
Hope someone finds it useful,