Is there a way to alter matching drag-and-drop for flat design?

I'm designing a course using flat design, and as you probably know, flat design has no beveling or gradients.

The only slides that don't match the rest of the course are the Matching Drag-and-Drop quiz slides and the Sequence Drag-and-Drop quiz slides.

Is there a way to tweak the formatting of the boxes to remove the beveling, the border, and make them one solid uniform color (instead of a gradient)?  

Thank you.