How to change the 'Subscribe' button's background color to theme color

FYI I am already using the background setting in Colors > Buttons but it doesn't do anything to the 'Subscribe' button of the Newsletter plugin.

Hi there,

The color of that button is coming from the Newsletter plugin and it's overwriting the theme settings:
https://www.screencast.com/t/b9Bs1OP4LTS

Does the plugin provide options to change that?

If not you can try this CSS:

.tnp-widget-minimal input.tnp-submit {
    background-color: #ffffff;
    color: #000;
}

Adding CSS: https://docs.generatepress.com/article/adding-css/

The CSS you provided works perfectly. Many thanks.

No problem :)