How to change background color of widgets?

[NiiightmareXD]

Hi I created a theme using:

       Theme::custom(theme::Palette {
            background: color!(0x121212),
            text: color!(0xffffff),
            primary: color!(0x64ffda),
            success: color!(0x64ffda),
            danger: color!(0xcf6679),
        })

But the background color of progress bar and some other widgets doesn't look that good:

How can I change the color?
Thanks for helping.

[NiiightmareXD]

I found out I have to manually create the theme