Fungus and yeast infections:
If all four feet are red then I would suspect a fungus. Fungus and yeast infections can be cured with medications.

If you look between the paws of the feet, you can see if they are clean and a regular skin color or if they are swollen, inflamed and pink looking.

If you see your dog licking them constantly you can try this.

Put Fido in the bathtub and wash his feet with an antibacterial shampoo for dogs, you can even use human dandruff shampoo.

Then drench the feet in 1 part apple cider vinegar to 1 part water and soak the feet in this solution. Do not dry the feet with a towel but let them air dry.

The Vinegar kills the yeast bacteria. Do this 2 to 4 times a day for the first week. See if there is improvement. You have to be diligent.

If your dog just will not leave his feet alone while the vinegar is drying, hold him in your arms until the feet are dry.