ADA Compliance: Contrast Ratio

We've been told the search box on our website using Catch Responsive theme doesn't meet ADA compliance for contrast ratio because the text in the box is too light on the search box background color. I can't find anywhere in the theme settings to change either the search box colors or the color of the default text in the search box. Is this possible? Or do I need to go into the CSS? What would the CSS tag be for these elements? Thank you! website: ci3t.org