There are two kinds of tool painter, it seems. The one we really want to avoid is the guy who wants to dress up old tools, and/or hide defects.
The other kind is the fellow who wants his tools to be easily identifiable, so they don't wander on the job (one theater carpenter I knew painted all his lavender, and never lost a tool on the job), or so they are easy to find in the shop. Red things are always easy to find in a shop, and that's the color I find most often. Chevy engine orange would also stand out.