Changing colors of the boxes around the fields

Contact Form 7 works great, thanks.

But I have one little issue. The color of the text is too close to the color of the background. I can live with that, but this color is also used to draw the lines around the boxes where the user enters his details. It’s difficult to see where each box is without those lines.

How can I change the color of these lines that define the input fields?

Thanks

https://wordpress.org/plugins/contact-form-7/