I have a short coated breed, and one of my bitches is white. She started licking her feet a lot a few months ago, and now has nice brownish/pink feet!! I have tried using bitter spray, to absolutely no avail, she is not at all put off by it. She doesn't bite or chew, there is no damage to her feet, just this horrid coloured feet.
Any suggestions please?

Is it all her paws, just her front ones or just her back ones? You need to find out what's causing her to lick her feet; once you've cured the reason (it could be an itch due to mites, for example) then the licking will stop, unless it's gone on so long it's become a habit.

Our Boston done this, to one or both of her back feet not her front we took her to the vet I said that she had been scratching her ears recently he said that some dogs to be a bit horrid like the taste of ear wax gross I know,her ears were looked at incase of ear mites or infection neither found he gave me some Surolan drops as she had started a fungal infection in her feet by the licking,these drops were rubbed in between her toes as instructed and also put in her ears as they contain anti inflammatory and antibiotic.Debby

Have you had her anal glands checked?  I have one that licks her toes/feet like this when her anals need emptying.