Weird one...coloring stainless

[Kozzy]

In the real world rather than the blacksmithing world, we do parts that are used in large food processing plants, generally from T304 stainless.

I had a weird one come up where the customer needs to be able to spot a specific tiny link on a long fast-moving chain so that the machine can be stopped at a proper location.  What they want is to color this specialized part on the chain blue (or some other easy to spot color except red or white variants).  Item has to be appropriately food grade for incidental contact.

Anyone have suggestions?  I am not even sure of a path to start digging.  What I see on the internet so far is not really conducive to do on a very small scale of onsies and twosies.  Ideally, I'd love to come out like a dyed aluminum anodized part, but even something with lesser coloring is better than nothing.  Magic marker (colored sharpies) won't stand up to the constant cleaning chemicals (tried that "KISS" suggestion already...gotta start with the easiest).  

The problem with standard bluing, graying or blackening is that the USDA inspectors will tend to have a little tantrum.  They see that range as "dirty" rather than coated.  Explaining doesn't cut it because inspectors change and well...are sometimes tyrants regardless of fact.

Any wild  XXXXXXX suggestions on where to start a search?  Some way to do the old fashioned "gold wash" easily that won't peel?  I'm open to ideas.

First suggestion is to watch your language

 

[Michael Cochran]

I did a quick online search and found reference to a process called 'inco-coloring'. It looks easy enough to accomplish, a little heat and moisture from what I found as I skimmed over the article.

[yahoo2]

http://www.rimexmetals.com.au/PDF_data_sheets/ChemicallyColouredStainlessSteel.pdf