peaches and cream
1. (hyphenated if used before a noun) Of skin (especially on the face), very fair, clear, and soft, especially with a rosy hue. I've heard that women in older times actually bathed with milk to maintain a peaches-and-cream complexion.
2. Of a situation, transpiring, progressing, or unfolding exceptionally easily or well. Our company had a bit of a rocky start, but everything's been peaches and cream for the last few months.
you're a peach
You are wonderful and/or helpful. You brought me coffee? Ah, you're a peach. Thank you much for picking up the cupcakes on your way to the party—you're a peach.