Theme color problems

I am using GridMarket as a theme and MarketPress plugin. Everything is working good execpt the color scheme. My customers are stating that they are having problems with seeing the input fields when they are checking out. Example: Enter your shipping information. Name, email, phone number, etc. They state that they can see the writing but the can not see the areas where you type you input in.

Can we change the color of the broader of the input field or make it darker so it is easier to see?