Julio Potier

This plugin adds 4 more colors into your admin/member profile. It changes the “4 squares preview” with a beautiful gradient preview. You can click on it to select the teme : it changes in real time to preview colors ! 
I added 4 icon themes for your admin menus, same behavior : click on it to preview.

BAW Better Admin Color Themes

Add more color themes and icons into your admin dashboard ! You can preview theme just clicking on it (JS required).

silver530

A light-weight plugin to change WordPress admin style into its own dark color scheme.

BossAdmin

A dark style color scheme for WordPress admin.

BAW Better Admin Color Themes vs BossAdmin