I decided to public my fork of A1 theme, which I’m using on my private Redmine installation for projects management. It is a fork of original A1 theme by RedmineUP, with some adjustments and Redmine 3.3 compatibility fixes (original theme seems to no longer maintained and does not support new releases of Redmine).
The theme can be downloaded from GitHub. You can install it by extracting theme directory into
public/themes/ (final path to style sheet file should look like:
public/themes/a1/stylesheets/application.css) and enable it in Redmine admin panel. The theme is compatible with Redmine 3.3 (it should work with older versions of Redmine, but it was never verified).