Index: src/wp-includes/default-filters.php
===================================================================
--- src/wp-includes/default-filters.php	(revision 27231)
+++ src/wp-includes/default-filters.php	(working copy)
@@ -280,7 +280,7 @@
 add_filter( 'pre_option_gmt_offset','wp_timezone_override_offset' );
 
 // Admin Color Schemes
-add_action( 'admin_init', 'register_admin_color_schemes', 1);
+add_action( 'admin_init', 'register_admin_color_schemes', 1 );
 add_action( 'admin_color_scheme_picker', 'admin_color_scheme_picker' );
 
 // If the upgrade hasn't run yet, assume link manager is used.
Index: src/wp-includes/general-template.php
===================================================================
--- src/wp-includes/general-template.php	(revision 27231)
+++ src/wp-includes/general-template.php	(working copy)
@@ -2099,7 +2099,7 @@
  * @since 3.0.0
  */
 function register_admin_color_schemes() {
-	$suffix = is_rtl() ? '-rtl' : '';
+	$suffix = ( function_exists( 'is_rtl' ) && is_rtl() ) ? '-rtl' : '';
 	$suffix .= defined( 'SCRIPT_DEBUG' ) && SCRIPT_DEBUG ? '' : '.min';
 
 	wp_admin_css_color( 'fresh', _x( 'Default', 'admin color scheme' ),
Index: src/wp-includes/script-loader.php
===================================================================
--- src/wp-includes/script-loader.php	(revision 27232)
+++ src/wp-includes/script-loader.php	(working copy)
@@ -578,6 +578,11 @@
 
 	// Register a stylesheet for the selected admin color scheme.
 	$colors_url = false;
+	// It's possible this is run before admin_init, so we need to make sure color schemes are registered.
+	if ( is_admin() && function_exists( 'has_action') && has_action( 'admin_init', 'register_admin_color_schemes' ) ) {
+		register_admin_color_schemes();
+		remove_action( 'admin_init', 'register_admin_color_schemes', 1 );
+	}
 	if ( ! empty( $GLOBALS['_wp_admin_css_colors'] ) ) {
 		$color = get_user_option( 'admin_color' );
 		if ( ! $color || ! isset( $GLOBALS['_wp_admin_css_colors'][ $color ] ) ) {