Yes, you can adjust the brightness of Amber's LED or turn it off:
First, you will have to log into Amber OS using the following URL
This will search for Amber inside your local network and pull up the following screen
Then you will be able to access your Amber OS web GUI
Now that you are logged in navigate to Control Panel > General. Click on the Hardware tab. You can adjust the brightness level here and also enable/disable night mode. Click Apply when you're done.