Reply To: How to change background color in specific page (checkout)

Hello,

The Checkout page has the default class from WooCommerce end which is .woocommerce-checkout, so you can try using the following Custom CSS on your Site in place of the one you are trying earlier:

.woocommerce-checkout .website-wrapper .main-page-wrapper {
    background-color: #99E8D0;
}

Location to paste Custom CSS, go to Dashboard >> Theme Settings >> Custom CSS >> Global CSS section >> paste the CSS.

In this CSS, you can change the color hex code according to your choice.

Best Regards