There is also the option to highlight messages based on the assigned tag colour. To enable this:
- Go to Preferences and select Mail from the left menu.
- Near the bottom of the section labelled Displaying Messages, click to select the checkbox labelled "Set colour of messages and conversations according to tag colour".
Click and drag a tag onto a message or conversation to assign it a tag. Note that if multiple tags are placed on the same message or conversation, it will no longer highlight.
You can also choose to automate this feature by setting up a filter to assign tags.
2. In the left panel, you can specify a tag in your search among other options.