I see no evidence of it. Coating may help to preserve them, but lacquer, shellac, linseed oil, or anything else will scratch, wear and degrade, or flake off, and then need to be removed and reapplied. I think gently cleaning and oiling with a good gun oil is plenty. Case colors should last a very long time unless you physically remove them over time with abrasive dusts, salty perspiration, grimy gloves, or aggressive cleaning. Some waxes even contain very fine abrasive particles, and can polish out and damage that extremely thin color layer over time.
