How to use COLORS in clan chat
In your battles, you may have noticed some players with colored names. It was recently discovered that Clash Royale has some specialized markup that changes the color of the text. You should be very careful when using these color tags to change your player name. You can only change it one time and you could get stuck with an error. However, you can safely use these tags in clan chat.
Just surround the text that you want to color with these color tags:
Typing in these codes is a little cumbersome so I doubt you’ll use them enough for it to become annoying to anyone else. Have fun!
Source: Clash Royale Arena