I have imported a VRML model into Blender 2.74 with concentric shells made of polygon faces, each layer of shell is a distinct diffuse color. I am hoping to select faces by their color, then apply translucency or transparency to partly reveal the shell of another color within. I thought python would be a good approach, but when I try bpy.ops.object.select_... I don't see a method to select by color.
You don't need python here. Go to edit mode select a face with your desired color, press SHIFTG and choose
Alternatively you can also choose a material in the properties editor and hit select below, to select all faces assigned to that material.