You can change the color of the text being entered into the form by adding an HTML widget to your page and pasting in some code.
Here is the code:
<style type="text/css">
div.sys_yola_form input.text{
color: #000000;
}
</style>
You'll want to change the color hex code (e.g. #000000) to something other than white. For different color hex codes, please visit this page.