By default, the platform does not have this option. You can use the following CSS code. However, using the code will make the Subscribe Icon more visible to the users. 

Please follow the steps below:

    1. Go to BuddyBoss - Theme Options

    2. Under Custom Codes, enable CSS

    3. Append the following:

i.bb-icon-l.bb-icon-bell:hover {
color: red;
}

    4. Save changes.

Note: Any modifications are considered as custom work already. Know more about our Support policy here: https://www.buddyboss.com/support-policy/

Screenshots

Without Code:

With Code: