To format the Message of the Day (MotD) of your server with colors, you need to have the server in Advanced Mode.
In the “Server.properties” file, you can enter the MotD with color codes under motd=.
Example:
motd=\u00A75 My Minecraft Servermotd= \u00A71 My \u00A72 Minecraft \u00A7e ServerThese colors are available:
\u00A70: Black\u00A71: Dark Blue\u00A72: Dark Green\u00A73: Dark Aqua\u00A74: Dark Red\u00A75: Dark Purple\u00A76: Gold\u00A77: Gray\u00A78: Dark Gray\u00A79: Blue\u00A7a: Green\u00A7b: Aqua\u00A7c: Red\u00A7d: Light Purple\u00A7e: Yellow\u00A7f: White