Need help with a Color Font

Hello! I want to create a color font. I already used the color font tutorial and created two Masters. If I overlay text-boxes in InDesign I get the combined effect – so the tutorial worked.
However I want that effect on a website, so I need to have ONE fontfile, that consists of BOTH masters combined. I want the XTrude-master to always ba black and at best be able to change the color of the top-master.
Is there any way to achieve this?
Kind regards and cheers!

Then you need to follow the COLR tutorial.