Use rgb color values for Markdown quote styling

Workaround as using hex values for colors starting with # introduces
unwanted side effects.

Fixes #24233

plugins/MantisCoreFormatting/core/MantisMarkdown.php

@@ -169,7 +169,7 @@ private function __quote( $line, $block, $fn ) {
 
 		if( $block = call_user_func( 'parent::' . $fn, $line, $block ) ) {
 			# TODO: To open another issue to track css style sheet issue vs. inline style.
-			$block['element']['attributes']['style'] = 'padding:0.13em 1em;color:#777;border-left:0.25em solid #C0C0C0;font-size:13px;';
+			$block['element']['attributes']['style'] = 'padding:0.13em 1em;color:rgb(119,119,119);border-left:0.25em solid #C0C0C0;font-size:13px;';
 		}
 
 		return $block;