I think needing it for insurance reasons is so very unlikely that its not worth worrying about. However, I would be worried about not having a receipt when it comes to submitting/doing your accounts.
Also this insurance thing: Say I had one red, one blue, one pink, one green etc. from an authorised dealer. Then every other bottle I had was bought from say... Ebay. In the unlikely event of a claim, is the client going to know the name of the colour I used on them? Couldn't I just say it was the one I bought from the authorised dealer? I'm not saying anyone should do this and I certainly don't, but it is a bit of a mine field and not quite as cut and dry as many people seem to think.
Incidentally, my insurance states that as long as I "do not knowingly buy or use a counterfeit product" I am covered.