Gradient Merge Google Calendar™ by Limonkufu

This extension also uses the user defined colors of each calendar to create a beautiful gradient for each event.

After installation refresh your Google Calendar, click on the plugin to change different settings

Source code: https://github.com/limonkufu/gradient-gcal-event-merge

Modified from: https://addons.mozilla.org/en-US/firefox/addon/google-cal-event-merge/