I have been trying to read what Wittgenstein writes about Augustine and the shopkeeper and the rest as if for the first time, but also slowly and carefully. As well as the danger of failing to do this, of not being careful enough, there is also the danger of going too slowly, trying too hard to be careful, and seeing things or imagining problems that are not really there. But Wittgenstein advised philosophers to take their time, so I think that slowly is the right way to read him. (This does not guarantee success, of course.)
Another danger is that of being influenced by others one has read, including Wittgenstein himself. If we have already been convinced that meaning and use are closely related, perhaps even the same thing, and that explanations do indeed come to an end somewhere, then we might be too unquestioning of the shopkeeper example. If we have read Stephen Mulhall on this example (in Inheritance and Originality or Philosophical Myths of the Fall--the relevant pages can be read online using either Google Books or amazon's "look inside" feature (search for "shopkeeper)) then we might be too quick to regard the shopkeeper as mechanical or zombie-like. Perhaps I have made that mistake.
So let me try to treat the example as realistic. People do use written notes in shopping sometimes. Online shoppers send written lists to shops, in places where goods are hard to find one might hand one's shopping list to the shopkeeper, foreigners might write down what they want, and so on. We can imagine the apples being kept in a drawer of some kind of refrigerator, with different draws for different fruits. People do count out loud, or under their breath. Looking up "red" on a chart sounds a bit odd, but wouldn't be if there were many similar colours (think of all the redlike paint shades you can buy). But we do, I think, have to imagine quite a bit to make the story credible as a scene from anyone's actual life. Wittgenstein has not done anything like this with the quotation from Augustine. Should he have, or is it OK, when doing philosophy at least, to ignore or forget about context?
This remains to be seen as far as the Philosophical Investigations goes. (Or so it seems to me.)