The theme component changes the style of the personal message posts to bubbles to help distinguish them from topics.
Settings:
- Set the colour of the bubble to your theme's primary, secondary or tertiary colors, or a selection of other common colors.
- Select different colors to help distinguish the messages you send from the messages sent to you.
- Set the background opacity of the bubble - the larger the percent the deeper the color.
- Choose whether to display the message bubble in a box shadow.
- Optionally append text to the Message Reply button to distinguish it from the Topic Reply button.
To learn more, check out: https://meta.discourse.org/t/personal-message-bubbles/147994