WordPress Rainbow Bar

rainbow-bar.php

<?php

/*
 * Plugin Name: Rainbow Bar!
 */

function rainbow_bar() {
?>
	<style type="text/css">
		#wpadminbar {
			background: linear-gradient(
				to bottom,
				#e24c3e 0%,
				#e24c3e 16.66667%,
				#f47d3b 16.66667%,
				#f47d3b 33.33333%,
				#fdb813 33.33333%,
				#fdb813 50%,
				#74bb5d 50%,
				#74bb5d 66.66667%,
				#38a6d7 66.66667%,
				#38a6d7 83.33333%,
				#8c7ab8 83.33333%,
				#8c7ab8 100% );
		}

		#wpadminbar,
		#wpadminbar .quicklinks > ul > li {
			-webkit-box-shadow: unset;
			-moz-box-shadow: unset;
			box-shadow: unset;
		}

		#wpadminbar .ab-top-menu > li > a {
			background-color: rgba( 50, 55, 60, .85 );
		}
	</style>
<?php
}
add_action( 'wp_before_admin_bar_render', 'rainbow_bar' );