More Hats

Alright, so for a blog entitled "Standard Hat Rules Apply", the standard hat rules sure haven't applied very much here, so it's time to remedy that. Here is a problem I first learned on the forums over at xkcd.
Consider a room of seven people around a table. They will each be assigned hats from seven different colours (ROYGBIV colours for definiteness, if you like). Hat colours may repeat, it is possible everybody will be given a blue hat or something. Standard hat rules will apply.

They must each simultaneously guess what their own hat colour is. If anybody is correct, everybody wins and are all given kittens. If everybody is incorrect they all lose and no kittens will be awarded, also the players will be killed. They may strategise before the hats are assigned. What is a strategy that guarantees victory (and thus kittens)?

Solution next time.

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