Have IITC CE installed in Tampermonkey or similar userscript manager.
Install the plugin, then go to Ingress intel and on the sidebar where all the plugin options are, you'll find Themes, click it and pick a theme
Light colored theme
Various color options to choose from
A lot of commonly available plugins have been touched up. Contact me if a plugin you use needs to be themed
Falenone in Telegram or here through Github