Okay, I think we may need to clarify some things. I think you are calling any type of data input a module, which isn't the case. Modules are things like the Blog, Forum, Event Calendar, HTML Content Module.
By default, all input fields have a white background. But, if you are using an Artisteer skin, you may have differently colored input fields. In this case, you need to copy any form element (input, select) in the style.css to the style-artisteer-overrides.css file. Once there you need to add "background-color: white;" to the form element selectors.
If you aren't using an Artisteer skin, just find any form element selector in your style.css and change the background-color to white.