Message in attachment format has wrong left border color in version 3.0

Troubleshooting
1

There is a bug when posting message in attachment format with named color style, as screenshot below, the good style .attachment__container--good should be #00c100 (green) but was overridden by the .app__body .attachment .attachment__container which is #2f81b7 (blue).

2

Thanks @bigsan, appreciate the clear report.

Anyone in the community interested in helping with a pull request to fix this?

Could make a nice first contribution, or a quick project to learn about the code base,