Themes
Editor appearance and diagram appearance are separate.
The editor theme — light, dark or system — controls the interface. The diagram theme controls how your diagram looks, and the two are independent: you can work in dark mode on a diagram that will be printed on white paper.
Six diagram themes are available: Clean, Corporate, Soft, Technical, Monochrome and Sketch.
If you have restyled individual shapes, changing theme asks before overwriting them and tells you how many would be affected.