CSS of file upload button

Hi,

I got this simple code [file file-397] – nothing special to test this function.

I would like to customize the CSS of the button to upload a file.

In developer options I get this:

<p>
<span class=”wpcf7-form-control-wrap file-397″><input type=”file” name=”file-397″ size=”40″ class=”wpcf7-form-control wpcf7-file” accept=”.jpg,.jpeg,.png,.gif,.pdf,.doc,.docx,.ppt,.pptx,.odt,.avi,.ogg,.m4a,.mov,.mp3,.mp4,.mpg,.wav,.wmv” aria-invalid=”false”></span>
</p>

How can I get the css of the button changed?