modrep(molid, rep, style, sel, color, material):
Modify the style, atom selection, color, and/or material for the
specified molecule and representation. Any combination of the last
four arguments may be specified, using positional or keyword
arguments.
modrep(0,0,color='name') # Color the first rep of molecule 0
by name.
modrep(0,2, selection='name CA', material='Transparent')
# For the third representation of molecule 0, change
the atom selection to "name CA" and the material to
"Transparent"