I've had issues with both VS2017 and now VS2019 where applying my custom fonts/colour scheme is not maintained between sessions. The same trick worked in VS2019 as what I discovered in VS2017, so this time I'm blogging it! Basically, import your custom colour scheme as usual using the "Import and Export Settings" wizard. Now go to Tools > Options > General and switch the "Color Theme" to any other theme than the current one. Now switch the theme back. That's it! For some reason this seems to persist your customisation of the theme whereas without switching themes the changes get lost.