By default, BuddyBoss Theme/Platform has no built-in feature to change the expand Buddypanel icon color without affecting the Body Text color. This will require custom work as this will change the look and functional aspect of the product.
This can be done via a CSS snippet. Please follow the steps below:
1. Go to BuddyBoss > Theme Options
2. Under Custom Codes, enable CSS
3. Append the following:
.bb-icon-l.bb-icon-sidebar { color: #FF0000; }
4. Save changes.