Contact fill-in boxes

On this page: the boxes used are beige but opaque. Is it possible to set these boxes to some form of transparency, like the content area?

I’m not certain that this is a good idea as it makes it very difficult to read the text.

This is the CSS code:

.slug-contact input#name, 
.slug-contact input#email, 
.slug-contact input#field_1, 
.slug-contact textarea#field_3 
    background: transparent;

Thanks Daniel. The problems generated by an image as background are numerous.