Always make sure that your selected items are easily identified at a glance.
Changing the background color is a simple and accessible way to achieve it!
It makes the user experience better since the user can easily figure out which elements are already selected.
Use Better Link Button
Links are important and you need to treat their appearance nicely.
Use Consistent Buttons
Your design, and mostly your buttons, need to be consistent thought the user interface.
Direct User Attention with Media
Leverage visuals to direct user's attention As humans, we tend to follow another person's line of sight.