Some info I found through NFPA
With respect to frictional heat or sparks, it is recognized that there is a need to control sources of ignition, including mechanical sparks from hand tools, that have sufficient energy to ignite flammable vapors. Studies, anecdotes, codes, and referenced...
You can find European guideline here:
http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31989L0392:EN:HTML
It does't mention shape or color though
<short citation>
1.2.4.
Stopping device
Normal stopping
Each machine must be fitted with a control whereby the machine can be...
