Customize cognito UI verification code input

Hi everyone, I am using the cognito hosted-UI with a CSS customizaion. Everything looks nice, except for the "verification code" input that has a default white background, and inherits the white text color from the containing div. This results in a white-on-white input field. Unfortunately, I can not find any solution to fix this via the customizable CSS classes.

Can you provide some help please? Is there anything I can do to customize that field? The only solution I have is to change everything back to a clear theme, so che colors combination will look better, but I'm not very happy with this.

Thank you very much! Nik