§57

Someone might claim that red things can be destroyed (e.g. a fire engine might be blown up by a bomb) but red cannot be destroyed. This is why the meaning of the word 'red' is independent of the existence of a red thing. - This sounds like someone trying to cling on to some version of the Augustinian theory - where words have a meaning because they refer to some 'object' (in a broad sense - incorporating properties/universals) - but not to particular instances of some property (e.g. the redness of a fire engine).

Wittgenstein (kind-of) agrees - he says that it make no sense to say that the colour red is torn up or pounded into bits. But presumably Wittgenstein would want to say that this is a grammatical point rather than, say, a comment on the nature of redness. - He's not doing metaphysics here.

Wittgenstein nonetheless wants to claim that a name (such as 'red') might lose its meaning if all of the red things were destroyed and we forgot which colour the word referred to (amongst the colours that we could bring before our minds). In that case what has happened is that we've lost a paradigm. - We've lost a sample that played a role in the language game (i.e. it functioned as something like a rule - a standard by which we could decide whether something was red).

In §57 then, Wittgenstein is challenging metaphysical claims about simple objects being indestructible things which guarantee that a word has a meaning.