Support attributes such as underline for author/branch colors

**Is your feature request related to a problem? Please describe.**
These attributes are supported in some other colors, but not for authors/branches, unless I'm missing something. I don't think I am as arrays are not accepted for these and trying e.g. `underline green` or `green underline` results in blank output.

This would help with separating e.g. subteams in a project, if you still want separate colors for people within subteams.

**Describe the solution you'd like**
Allowing usage of arrays like in other color options would be the most consistent solution.

**Describe alternatives you've considered**
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**Additional context**
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