How to set custom colors for the code editor

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I'm playing around with code I copied straight out of the code editor demo, and I want to add some custom colors. I couldn't find any documentation, so I'm going through the code itself to guess. Just to see if I can do it, I'm creating a custom SyntectSettings value, like this:

        let mut highlight_settings = SyntectSettings::default();
        let mut theme = Theme::default();
        theme.settings.background = Some(Color { r: u8::MAX, g: 0, b: 0, a: 0 });
        _ = highlight_settings.ts.themes.insert("Homemade".to_owned(), theme);

I've got as far as changing the layouter code from the original:

        let mut layouter = |ui: &egui::Ui, buf: &dyn egui::TextBuffer, wrap_width: f32| {
            let mut layout_job = egui_extras::syntax_highlighting::highlight(
                ui.ctx(),
                ui.style(),
                &theme,
                buf.as_str(),
                language,
            );
            layout_job.wrap.max_width = wrap_width;
            ui.fonts(|f| f.layout_job(layout_job))
        };

To this:

        let mut layouter = |ui: &egui::Ui, buf: &dyn egui::TextBuffer, wrap_width: f32| {
            let mut layout_job = egui_extras::syntax_highlighting::highlight_with(
                ui.ctx(),
                ui.style(),
                &theme,
                buf.as_str(),
                language,
                &highlight_settings
            );
            layout_job.wrap.max_width = wrap_width;
            ui.fonts(|f| f.layout_job(layout_job))
        };

But now, I can't figure out how to use that new theme. The &theme argument is a CodeTheme, but with the syntect feature on, the only thing I can set on that struct is a dark mode boolean, and a syntect_theme enum which doesn't include an option to set it by name.

So, does anybody know how do I use a custom color theme for syntect syntax highlighting?