Some Mac dialogs have keyboard shortcuts; Command-D for Don’t Save is probably the most common. One way to make these handy shortcuts a wee bit more discoverable is to display the Command symbol ? (what is sometimes referred to as the “flower”) and desaturate everything but the shortcut key letter when the Command key is depressed.
For the common Save dialog, you would see this when Command is held down:
The iTunes Info window:
Ellington & Coltrane together — what could be better?!
The relevant buttons would need to be resized to comfortably accommodate the Command symbol.