Responsive design, mobile first approach, vanilla JS, CSS

Hi everyone. This is my solution to the newsletter signup form. I'm focusing on accessibility and form validation. I still have an issue with styling the input field. In the solution, the initial state of the input field's background should be white and the border gray, but instead it displays the color for when the input is invalid. Could someone check my code and see where the issue is. I also appreciate any feedback on the overall code and links for material that can help improve my code. Thank you :)