Potato Guide #1

Using my laptop in daylight reveals gunge in & on the keyboard. Where does it come from? Obviously typing fingers leave a residue of skin cells & such, but there's some bright blue fluff in there that defies explanation. If it were beige or brown or green or pinkish I could put it down to detritus from some snack shoved into my gob while browsing for recipes, failing to learn Czech at U Gandalfa, looking up weird breeds of cats, cacking myself at far more interesting blogs than this, or playing solitaire. But bright blue? Blue food is pretty rare. It could be lint, but from what? Bright blue's not a colour seen much round this house. Where are the cotton buds?