[PyMOL] movie frame alterations

Is it possible to make changes to the way individual frames are rendered?
Specifically, I'm writing a Python script (translated literally from C,
but I'm too tired to learn the Python API right now) to evaluate bond
"quality" and highlight the distorted regions in a frame of a protein
morph.  However, since the distortions tend to come in the middle of a
morph, I want to examine each frame alone and apply highlighting only
where applicable.

Right now, treating individual frames as part of an object (i.e. for a
movie) means that calls like 'color red, 101/ca' are applied to every
state.  Is there some way to only run that command on one state?  In
simple terms, I'm trying for a movie that changes color during its course
to indicate bond quality.  It's much easier to do this if I can use movie
objects, especially since it would be nice to be able to run this
interactively.  Otherwise, I'm going to just create a very long pml file
with all the commands.

thanks,
Nat