You can edit the design of your chat window in different ways:

• You can change the color of the chat bubbles if you go to Settings > Messages > Message theme. You'll find more information about this in the article How do I use colored message bubbles?.
  
  
• You can decide if you want to align messages to the right or to the left. If you go to Settings > Messages > Display options and tick the box Align my sent messages to the right, your messages will be aligned to the right and the visitor's messages to the left. If you don't tick the box, all messages will be aligned to the left.