Change loading screen color in Rokophoto

Install  https://wordpress.org/plugins/simple-custom-css/, go to Appearance -> Custom CSS the add the following snippet:

#preloader{
background-color: #ccc;
}

Save your changes and you're done.

You could edit the value to any of your choice, you could find hex color codes by using this tool:  www.hexcolortool.com

Your loading gif would still be on a white background, this might not blend with your new background color so you could replace it by going to the img folder within the theme folder and replacing loading.gif with your gif of choice or delete it.