How to change the color of the submit button in mobile responsive

The color in the form builder is the same for both desktop and mobile. You currently set the color to white which should do it. Please check the form with your actual device to see if the issue persists.

Below a screenshot of your settings:

Hi, what I meant was that the submit button is hidden behind the progress bar, the bar that shows the back button. so thats not sure friendly. the submit button should be shown independently. 

Unfortunately, that is how the Submit button of card forms display by default on mobile devices. As mentioned by my colleague, you can customize the background color of buttons and text color of the submit button accordingly.