Color coding your locks is a good way to distinguish different locks for different shifts, or departments. Just know each person has to have their own identifiable lock. If you have a small group of people who are performing lockout functions, then you get use a color coding so long as EVERYONE knows the green locks belong to Bob. However, if you have a lot of people who will be performing lockout, then you still need to have a way to identify whose lock is being used to lockout.
Just be aware of some of the faults of color coding. If you color code by shift, and one of your maintenance guys is covering for someone else, s/he will have different color lock than everyone else. Coloring by department generally works better, having maintenance use red locks, and production use blue. But again, make sure whoever is working on the equipment has their name clearly identifiable to everyone else around the equipment.