Weird looking skin on paw - what could this be?

I found this on Pip the other day, and it looks very strange. The skin is kind of bluey-grey (which may just be the colour of her skin when the fur falls away) and the fur seems to be coming off too. I touched Pip all over her paw and she doesn't seem to have any discomfort from it, and she isn't overgrooming it or protecting this paw in any way. She seems perfectly happy.

I have tried Googling it but can't find anything which resembles this. 

Could this be some kind of fungal infection?

Not too sure... It almost looks like a bruise but that wouldn't explain the hair loss unless she's licking her foot excessively. Could be natural skin pigment too. Maybe you could shave a bit of her other foot to see if it's the same color. Sorry I'm not more helpful... I'm a bit baffled by it too.