Experiment with the settings to accustom the highlighting to your own taste.
If color gradient is disabled %color is set to newer comment color. Otherwise it takes a value between newer comment color and older comment color based on the age of the comment. By default newer comments will have more intense colors while older comments will have lighter colors.

If you're updating from an earlier version, make sure you reset your settings first to ensure it will work properly.
To use this on Chrome with Tampermonkey, make sure you enable following flags:

chrome://flags/#enable-javascript-harmony
chrome://flags/#enable-experimental-web-platform-features

Comments screenshot:

Settings screenshot: