diff --git a/tests/phpunit/tests/admin/includes/ajax-actions/saveUserColorScheme.php b/tests/phpunit/tests/admin/includes/ajax-actions/saveUserColorScheme.php
new file mode 100644
index 0000000000000..cfcbe149e29e4
--- /dev/null
+++ b/tests/phpunit/tests/admin/includes/ajax-actions/saveUserColorScheme.php
@@ -0,0 +1,171 @@
+<?php
+
+/**
+ * Admin Ajax functions to be tested.
+ */
+require_once ABSPATH . 'wp-admin/includes/ajax-actions.php';
+
+/**
+ * Testing wp_ajax_save_user_color_scheme() functionality.
+ *
+ * @package WordPress
+ * @subpackage UnitTests
+ * @since 3.8.0
+ *
+ * @group ajax
+ *
+ * @covers ::wp_ajax_save_user_color_scheme
+ */
+class Tests_wp_ajax_save_user_color_scheme extends WP_Ajax_UnitTestCase {
+
+	/**
+	 * Administrator user ID.
+	 *
+	 * @var int
+	 */
+	protected static $admin_id;
+
+	/**
+	 * Setup test fixtures.
+	 *
+	 * @param WP_UnitTest_Factory $factory
+	 */
+	public static function wpSetUpBeforeClass( WP_UnitTest_Factory $factory ): void {
+		self::$admin_id = $factory->user->create( array( 'role' => 'administrator' ) );
+	}
+
+	public function set_up(): void {
+		parent::set_up();
+		add_action( 'wp_ajax_save-color-scheme', 'wp_ajax_save_user_color_scheme', 1 );
+
+		// Hook into wp_die to prevent execution from stopping.
+		add_filter( 'wp_die_ajax_handler', array( $this, 'getDieHandler' ) );
+	}
+
+	public function tear_down(): void {
+		remove_filter( 'wp_die_ajax_handler', array( $this, 'getDieHandler' ) );
+		parent::tear_down();
+	}
+
+	/**
+	 * Returns our custom die handler.
+	 *
+	 * @return callable
+	 */
+	public function getDieHandler() {
+		return array( $this, 'dieHandler' );
+	}
+
+	/**
+	 * Custom die handler that throws an exception.
+	 *
+	 * @param string|WP_Error $message
+	 */
+	public function dieHandler( $message ) {
+		$this->_last_response .= ob_get_clean();
+
+		if ( '' === $this->_last_response ) {
+			if ( is_scalar( $message ) ) {
+				$this->_last_response = (string) $message;
+			} else {
+				$this->_last_response = '0';
+			}
+		}
+
+		if ( '-1' === $this->_last_response || ( is_int( $message ) && -1 === $message ) ) {
+			throw new WPAjaxDieStopException( $this->_last_response );
+		}
+
+		throw new WPAjaxDieContinueException( $this->_last_response );
+	}
+
+	/**
+	 * Tests success for wp_ajax_save_user_color_scheme().
+	 *
+	 * @ticket 65252
+	 *
+	 * @dataProvider data_save_user_color_scheme_success
+	 *
+	 * @param string $color_scheme The color scheme to save.
+	 */
+	public function test_save_user_color_scheme_success( string $color_scheme ): void {
+		wp_set_current_user( self::$admin_id );
+
+		$_POST['nonce']        = wp_create_nonce( 'save-color-scheme' );
+		$_POST['color_scheme'] = $color_scheme;
+
+		// Set an initial color scheme to check if it changes correctly.
+		update_user_meta( self::$admin_id, 'admin_color', 'fresh' );
+
+		try {
+			$this->_handleAjax( 'save-color-scheme' );
+		} catch ( WPAjaxDieContinueException $e ) {
+		}
+
+		$response = json_decode( $this->_last_response, true );
+
+		$this->assertTrue( $response['success'], 'AJAX response should be successful' );
+		$this->assertSame( 'admin-color-fresh', $response['data']['previousScheme'] );
+		$this->assertSame( 'admin-color-' . $color_scheme, $response['data']['currentScheme'] );
+		$this->assertSame( $color_scheme, get_user_meta( self::$admin_id, 'admin_color', true ) );
+	}
+
+	/**
+	 * Data provider for test_save_user_color_scheme_success.
+	 *
+	 * @return array<string, array{
+	 *     color_scheme: string,
+	 * }>
+	 */
+	public function data_save_user_color_scheme_success(): array {
+		return array(
+			'default scheme' => array(
+				'color_scheme' => 'fresh',
+			),
+			'light scheme'   => array(
+				'color_scheme' => 'light',
+			),
+			'coffee scheme'  => array(
+				'color_scheme' => 'coffee',
+			),
+		);
+	}
+
+	/**
+	 * Tests failure for wp_ajax_save_user_color_scheme() with invalid color scheme.
+	 *
+	 * @ticket 65252
+	 */
+	public function test_save_user_color_scheme_invalid_scheme(): void {
+		wp_set_current_user( self::$admin_id );
+
+		$_POST['nonce']        = wp_create_nonce( 'save-color-scheme' );
+		$_POST['color_scheme'] = 'non-existent-scheme';
+
+		try {
+			$this->_handleAjax( 'save-color-scheme' );
+		} catch ( WPAjaxDieContinueException $e ) {
+		}
+
+		$response = json_decode( $this->_last_response, true );
+
+		$this->assertFalse( $response['success'], 'AJAX response should be unsuccessful for invalid color scheme' );
+	}
+
+	/**
+	 * Tests failure for wp_ajax_save_user_color_scheme() with invalid nonce.
+	 *
+	 * @ticket 65252
+	 */
+	public function test_save_user_color_scheme_invalid_nonce(): void {
+		wp_set_current_user( self::$admin_id );
+
+		$_POST['nonce']        = 'invalid-nonce';
+		$_POST['color_scheme'] = 'fresh';
+
+		$this->expectException( WPAjaxDieStopException::class );
+		$this->expectExceptionMessage( '-1' );
+
+		$this->_handleAjax( 'save-color-scheme' );
+	}
+}