...it should work, you're probably using the wrong pallet...
loading unit's grp steps:
1. click on Load External File and browse for the grp
2. click on Load Pallet and search for the SC_Unit_Palette.pal
for icons:
same as units, but use the Cmdicons_Pallet.pal instead of it
for everything else:
just keep switching pallets until you find a pallet that matches the graphic and makes it look normal.