By default the background color will be the same as the warning color, but with 1% opacity. If you want to change the background to a different color, it will require custom work. However, our team was able to create a workaround for you.
Please follow the steps below:
1. Go to BuddyBoss > Theme Options
2. Under Custom Codes, enable CSS
3. Append the following:
body #buddypress p.warning {
background-color: #ff0000;
}
4. Save changes.