This is a browser extension that colors event titles in the new Google Calendar according to your chosen color for each calendar (more like the old Calendar, pre-2018).
NOTE: With manual installation, the extension will not be automatically updated. You'll need to update it manually to get newer features. Also, if you switch to the version from the Web store, you should uninstall the manually installed version.
Download a zip file of this project by clicking here, and unzip the files. Go to chrome://extensions/, enable developer mode (checkbox at the top), click "Load unpacked extension...", and select the unzipped directory. Reload your Google Calendar tab.
Download a zip file of this repo by clicking here, and unzip the files. Go to about:debugging and click "Load Temporary Add-on". Select the manifest.json file in the unzipped directory.
I think this extension should work in most up-to-date desktop browsers (this probably does not include Internet Explorer). I don't know how to install it on anything but Chrome and Firefox. Google it! If you figure it out and want to help, write up the instructions and submit a pull request (or file it as an issue above if you don't know how to do that).