Unable to add Colour Schemes to Dawn 11.0 Theme

Im trying to move from Dawn V9 to V11.

But when i create the new theme file, i lose all my existing colours and am unable to create new colour schemes.

I have tried following the guide for updating theme colours but it appears im missing the option and i dont know why of if i have done something wrong.

Im getting the below error messages in the edit view of the theme.

I have the exact same problem… I’ve checked the settings_schema.json and settings_data.json files and they already have my sites colours added in… so I’m not sure how to get it to simply display my site as usual… is it a bug?