I have an icon that looks like a chat bubble to send a message to a user. Now, you can send a message both to an online and offline user. I'm trying to have two different icons.
Right now they are only separated by color, where the online icon is filled with green. However, I want a visual indicator that is not dependent on color.
I have considered adding a slash over the icon but then I'm afraid the users will believe that you can't send a message to a offline user. Any suggestions?