Why are my French Bulldog's eyes different colors and look drowsy?

Thank you for providing the pictures of Piggy they were very helpful! It can be a normal variation from dog to dog on the color of scleras. While yes, they are typically white with some blood vessels present, some dogs may have different concentrations of pigment cells (melanocytes) that can make some sclera darker than the other or even just a portion of it. It will be important to take Piggy to see your veterinarian or an ophthalmologist if you notice him squinting his eye, scratching at it, increased tear production (weepy eye) or you notice that he has any obvious defects on the surface of his eye. These signs usually indicate irritation or damage to the eye and can be quite painful for Piggy or others.