change calendar color

how can i apply/change the orange in the calendar for the "BuddyPress Group Calendar" plugin ?
I managed to use "inspect element" in Safari to see the change live, but what would be the exact CSS code to apply in my theme ?
i am currently using Kleo theme locally on MampPro.
the theme has the option to apply custom CSS.
(the screenshots shows the plugin and inspect element - i changed text using Ultimate Branding)

any kind assistance would be greatly appreciated,