WordPress: set default admin color scheme and get current or all admin color schemes.

wp_admin_color_scheme.php

<?php

/**
 * Set the default admin color scheme for WordPress user.
 */
add_filter('get_user_option_admin_color', 'set_default_admin_color');
function set_default_admin_color($result)
{

	// set new default admin color scheme
	$result = 'midnight';

	// return the new default color
	return $result;

}

/**
 * Get the current admin color scheme from WordPress user.
 */
add_filter('get_user_option_admin_color', 'get_current_admin_color');
function get_current_admin_color($result)
{

	global $_wp_admin_css_colors;

	// get current admin color scheme name
	$current_color_scheme = $result;

	// get all available colors from scheme name
	$colors = $_wp_admin_css_colors[$current_color_scheme];

	// now you can use this colors or store it
	// var_dump($colors);

	// important: we should return the default color scheme
	return $result;

}

/**
 * Get all available admin colors schemes from WordPress user.
 */
add_filter('get_user_option_admin_color', 'get_all_admin_colors');
function get_all_admin_colors($result)
{

	global $_wp_admin_css_colors;

	// get all available color schemes
	$colors = $_wp_admin_css_colors;

	// now you can use this color schemes or store it
	// var_dump($colors);

	// important: we should return the default color scheme
	return $result;

}