You've Selected it... Now Do Something With it!

Link to the official Rasmol Manual, chock full o' commands for your scripting pleasure.
In these scripts, I have selected the "A" chain of cytochrome c, with the command select *:a
Turn Chain A Purple  color purple
Render Chain A as Ribbons  wireframe off ; ribbons
Render Chain A as a Space-Filling Diagram  ribbons off ; spacefill
Turn Chain A back the way it was  spacefill off ; wireframe ; color cpk
Another Really Cool Trick...
Multiple selects can be used in the same command line, as this example demonstrates:

make chain A purple ribbons, while making chain B red spacefill...

select *:a ; wireframe off ; ribbons ; color purple ; select *:b ; wireframe off ; spacefill ; color red