A light ring is a great way to do it, though consider when you choose your color what colors are likely to be in the environment
If you are just using the stock example, take a look at the NI Vision Assistant, it's a handy tool for tuning the vision detection algorithm for your situation. You'll want to play around and find what works best for your lighting situation.
Theres alot of great information in the NI Vision white paper for how to setup the vision assistant as well, and be sure to tune the settings on your camera (like the brightness) to get the best results.