Hi, im getting this error on my error_log joomla, can anyone help me what is this?

PHP Notice: Undefined variable: social_style in /home/feyrimx/public_html/templates/j51_elvira/php/styles.php on line 141

opening the file styles.php have on the line 141 this

#socialmedia ul li a [class^="fa-"]::before, #socialmedia ul li a [class*=" fa-"]::before {color: <?php echo $social_style; ?>}