Colored finish on 5/8 inch steel balls

adv.
We can color anodize 420 stainless steel.

A. One way would be to contact a local gun store or on-line ammunition dealer. Ask for 18 or 20 gauge colored steel shot, it might be a special order because usually the colored shot is more readily available in 12 gauge. Waterfowl Magazine published an article related to this topic on July 28, 2011. The piece was written by L.P. Brezny. The article mentions brand names.

A. Correction:
I double-checked the sizes and the gauge mentioned (18/20) is way too small for you, my apologies. You might get away with the color anodizing as proposed by the O.P., it depends on your application. Here are three more durable options:
1. The best option would be to work with a reputable machine shop or manufacturer and write them a specification. They will probably charge $500-1000 depending on the quantity and other factors. This would give you very good quality.
2. Another option to save money would be to go buy ball bearings of the desired size. These are widely available from industrial distributors. Then take the ball bearings to a painting company or a coating company. The painting companies will probably charge less and do the work more quickly but the coating companies will likely give a more durable finish. Write a specification.
3. The cheapest and dirtiest option would be to buy the ball bearings and different colors of fingernail polish. You will also need a can of elbow grease.