Made for Diigo v1.0.2007041901

The script is a prototype, it changes the background color of highlights and annotations to whatever colors you choose.
You can also:
-Specify a color for a specific user's highlights. (It is disabled by default, you need to uncomment a few lines...)
-Specify colors for the search-term highlights. (It is disabled by default, you need to uncomment a few lines...)

The default colors in this script are not very beautiful, so I recommend choosing the colors by yourself! Perhaps you will share your palette in the comments section.

I don't believe this script is very light-weight to be run as a global Stylish-script, but it should work if you are inclined to run it. :)

Feel free to optimize the script.
Feel free to publish alternative color palettes for Diigo by using this script.

Note: This script only modifies the background-color. This means that it will not work if you use underlining and font-color change as highlighting type in Diigo.