I've done a search and can't seem to find much about the Colortune spark plug tool for diagnosing idle mixture(other than someone asking about it (as I am) or someone stating what color theirs was showing)? Is this a tool that is worthwhile having in the tool box? Any one have any experience with this? I have a 47 1/2 ton with a Carter W-1. Thanks.

It's a small world, but I wouldn't want to paint it.