There is a hierarchy in which color at the model level is overruled by color at the residue level, which is in turn overruled by per-atom color settings.
The command rescolor sets color at the residue level. Even if only particular atoms are specified, the entire residue(s) containing the atoms will be affected. A color change at the residue level will not be visible, however, if color assignments at the atom level already exist. Using ~rescolor sets residue color to none (no color assigned).
Color_name is a built-in name or a name defined previously with colordef. A special color name is colorpanel, which refers to the color currently defined in the Color Editor.
Color sets colors at the atom level, and modelcolor sets colors at the model (or submodel) level; surfcolor sets which level is used as the source for visible surface colors. Rainbow also sets color at the residue level, but according to a rainbow gradient across each chain.
See also: color, modelcolor, rainbow, surfcolor, the Actions menu