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).

Greg Ross

Due to a bug in previous versions (of this plugin, you will need to deactivate, uninstall and then re-install to receive future updates.
Grey color schemes for the admin area of WordPress 3.8.
<ul>
<li>
‘A Touch of Blue’ – The Modern Grey theme with a blue hilight for the current selected menu item.
</li>
<li>
‘Classic Grey’ – The Classic Grey colour scheme from WordPress 3.7, a very light grey for menu items and white backgrounds.
</li>
<li>
‘Modern Grey’ – The new default color scheme from WordPress 3.8 lightened up!
</li>
<li>
‘Post Modern Grey’ – The Modern Grey theme with grey instead of blue buttons.
</li>
</ul>
Special thanks to the translators:
<ul>
<li>Spanish – Andrew Kurtis (www.webhostinghub.com)</li>
</ul>

Grey Admin Color Schemes

Grey color schemes for WordPress 3.8's admin area.

BAW Better Admin Color Themes vs Grey Admin Color Schemes