Why do Plums have that Grey Color on Their Skin, but when you Rub the Plum it reveals its Purple Skin?

Why do Plums have that Grey Color on Their Skin, but when you Rub the Plum it reveals its Purple Skin?

Why do Plums have that Grey Color on Their Skin, but when you Rub the Plum it reveals its Purple Skin?
A number of fruits, including grapes, secrete excess sugar through their skins when they're ripe. This can create a white or gray film, which is harmless and easily wipes or washes off.
Reply:Its dirt and environment and once removed and/or cleaned it shows the true color of the fruit.