Here’s a fun option:  the background color of the watchface will change its color along the rainbow according to the minutes of the hour:
►:00 blue
►:10 cyan
►:20 green
►:30 brown
►:40 red
►:50 purple
The color changes every minute to shades of the colors in between. So you can quickly glance at your watch, if it has a brown tint, you know it’s around half past the hour…