You can change the color of the ISSABEL top to match the rest of the GUI with this adjustment.
Example screen shot https://imgur.com/a/ZlpBxzD
sed -i -r 's/373e4a/522b76/' /var/www/html/themes/tenant/_common/_menu.tpl
From a command line. This will change the color "grey" to a matching "purple"
Grey= #373e4a Purple= #522b76