How do I highlight the field background with a different color for the different repeating phrases that appear in the content in each tiddler

[XYZ]

This can greatly improve the accurate grasp of each note content, so that the note content becomes shorter and refined, and reduce unnecessary repeated pronoun

The effect is achieved through the browser’s built-in search function

[pmario]

You should have a closer look a the core Dynannotate-plugin. There are some examples in the plugin.