Contact form style?

The text color style is coming from your theme, not the Gravity Forms styles. It's being output in a style block embedded in your page. View the source and you'll see this around line 140.

body, p,
h1, h2, h3, h4, h5, h6, h1 a, h2 a, h3 a, h4 a, h5 a, h6 a,
h1 a:visited, h2 a:visited, h3 a:visited, h4 a:visited, h5 a:visited, h6 a:visited,
ol.commentlist, #commentform input, input, #commentform textarea, textarea { color: #ffffff; }

That rule is setting everything, including your form input colors to white. If you disable that or change that, then you should be fine.

You can try overriding that rule by adding this to the end of your theme's style sheet.

body .gform_wrapper .gform_body .gform_fields .gfield input[type=text],
body .gform_wrapper .gform_body .gform_fields .gfield input[type=url],
body .gform_wrapper .gform_body .gform_fields .gfield input[type=tel],
body .gform_wrapper .gform_body .gform_fields .gfield input[type=phone],
body .gform_wrapper .gform_body .gform_fields .gfield input[type=password],
body .gform_wrapper .gform_body .gform_fields .gfield input[type=email],
body .gform_wrapper .gform_body .gform_fields .gfield input[type=submit],
body .gform_wrapper .gform_body .gform_fields .gfield select,
body .gform_wrapper .gform_body .gform_fields .gfield textarea {color:#000}

That should reset the text color to black on all of your Gravity Forms and not change anything else in your theme.