To give an example of this... When answering the first question, I found myself thinking only of things which are pure white almost all the time. So I thought o

To give an example of this... When answering the first question, I found myself thinking only of things which are pure white almost all the time. So I thought of snow, clouds, white sails - and even with those I felt they were arguable (snow can be grey; clouds too; sails can be multi-coloured). Arguably the only thing that's prototypically white in the world is sunlight - and that looks yellow! :-P On the other hand, when considering my fridge, I only thought of what is white-looking in there... Milk is prototypically white, but cheese, eggs, bread, mold on some old sausages, etc... are just kinda sorta white sometimes. But within the limits of a fridge they're acceptable examples of white. I think that's what the GP was arguing: when asked for "white things in the world" you naturally place the bar for "white" much higher than when asked for "white things in your fridge".