Time and color, combined into a screensaver!
This Mac OSX screensaver displays the current time and its RGB-color equivalent. In 24 hours the red-value goes from 0 to 255, the green and blue values do so in 60 minutes/seconds. So at midnight you’ll have black and at 23:59:59 you’ll have white. And in between you’ll find every other color in the RGB-spectrum.
The screensaver is available with either Helvetica Neue or a monospace font (Menlo).
If you don’t have a Mac or just don’t want to use a screensaver, you can visit the web version here (monospace) and here (Helvetica).