How do I ask my wife to take better care of her appearance

Ok let me start by saying I love my wife alot. She has gained some weight since we got married but the real issue is she doesn't put any work into looking nice. She is a stay at home Mom so I understand she doesn't feel the need to get all dolled up but i would love to see her with a bit of makeup, her hair styled and some less frumpy clothes. Everytime she does dress up or has her hair done I tell her great she looks. But it very rare. Her grey hair grows in and she waits a long time to go the salon, her feet are scratchy and the heels cracked and I just see other woman her age that look good. Us men are visual and I want her to look nice. How can I or should I tell her this.