Background colour

Hello, first of all I want to say thank you for the amazing theme you have provided for free in SimpleCrop. I would like to ask if there is a way to change the background colour. You have the option of choosing Light ______ or Dark ______. when you pick a light option the background is white but when you pick a dark option the background is dark grey. My question is… is there a way of changing the grey in the dark option to actual black?

Thanks

Stephen Solademi