I know there is an explanation at https://makecode.com/playground#basic-ns-color, but I don’t understand it.
Do you have an extension started?
To set the icon, you need to set a property on the namespace like this:
That “uf031” is a unicode character in the Font Awesome 4 library: https://fontawesome.com/v4.7.0/icons/
Specifically this character: https://fontawesome.com/v4.7.0/icon/font
Wow, coincidently, that was the exact icon I needed! Thanks!