shazdeh

This plugin adds an option page where you can add color options and the plugin hooks this elements to the Customizer where your client or theme users can customize the design.
Since 0.2 the custom designed panel to change colors is removed and now design tweaks are done through the WordPress Theme Customizer.

Color Manager

Enable your clients or theme users to easily change the color scheme of your design. With live preview!

Kyle Foulks

This plugin allows easy manipulation of WordPress admin menu colors and appearance. Users can color code menu items in the admin menu for ease of access. 
You can also hide any menu from view.

Easily Change Admin Color

Allows easy manipulation of Wordpress admin menu colors and more.

Color Manager vs Easily Change Admin Color