I have to admit that my understanding of the various commands to use for very specific functions in Chimera is difficult for me to find the correct command.

I know how to color a specific residue using the sequence table and the color chart.

So how do I color a specific atom in a residue. For example I am interested in coloring the nitrogen of the Asn amide side chain say color red. How can I do this?

When I highlight a residue and visualize it as a ball and stick, then color it different from the color of the helix, the color of that part of the helix changes to the color of the ball and stick, different from the color of the rest of the helix. 

How can I reset the color of the helix location of that residue, leaving the ball and stick as another color.

Thank you

Arthur Szabo

Professor Emeritus

Chemistry and Biochemistry

Wilfrid Laurier University

Waterloo Canada.