I use this one - https://themeforest.net/item/modern-responsive-admin-dashboard-template/11004840 - it is called Modern Admin and it really gives you a lot of functionality! It is flat-retina ready template for Wordpress admin. This plugin comes with 4 color schemes, custom login form, configurable menu & dashboard icons.
Here are the features of this great plugin:
Try Easy Admin Color Schemes - https://wordpress.org/plugins/easy-admin-color-schemes/ - you can change the colors there. You can also pick and use your very own color (with color picker). I like the purple theme! :-)
With https://wordpress.org/plugins/ag-custom-admin/ you can really re-brand your admin page and even the log-in page! :-)