https://www.theverge.com/2017/9/18/16308924/samsung-galaxy-note-8-live-messages-how-to-pen

One of the cool new features on Samsung’s Galaxy Note 8 is Live Messages, a fun new addition that lets you draw animated messages to send to your friends. To access live messages, simply take the S Pen out from the device, hit the grey pen icon that pops up, and select “live message.”

That’ll pop up the Live Messages window, where you can draw your own custom message. On the top left of the window, there are a couple of icons, each providing different options for the pen. The leftmost icon lets you choose between regular lines, a glowing effect, and a sparkling line effect that’s become the most well known of the three. There’s also options for changing how thick the lines are, and a choice of colors. When you’re drawing your message, be aware that you can mix pen sizes and colors, but everything has to be the same effect — so if you’re drawing in sparkling lines, everything has to be in sparkling lines.