By default, the platform does not have this option. You can use the following CSS code to add color to the BuddyBoss Member send icon.
Please follow the steps below:
1. Go to BuddyBoss > Theme Options
2. Under Custom Codes, enable CSS
3. Append the following:
#send-private-message .bb-icon-mail-small,
#buddypress .button-wrap.member-button-wrap.footer-button-wrap #send-private-message.generic-button .send-message i:before {
color: #B50000;
}
4. Save changes.