/* Change header color on AMP mode */
function add_custom_css_for_amp_mode() {
	?>
	/* Header Color */
	.amp-wp-header {
		background: linear-gradient(90deg, #3070b5 0%, #006838 100%);
	}

	/* Header Logo */
	.amp-wp-header .jeg_mobile_logo {
		background-image: url(https://upload.wikimedia.org/wikipedia/commons/thumb/2/2f/Google_2015_logo.svg/368px-Google_2015_logo.svg.png);
	}
	<?php
}
add_action( 'amp_post_template_css', 'add_custom_css_for_amp_mode' );