“SOLD” image or text over some gallery images

Is there a way to put a “SOLD” image or bold text over some of my masonry gallery images? I did try playing around with the caption settings. The closest I came to what I want was to Display Excerpt/Display as centered overlay/Always display. Is there a way to make that then display larger, bolder, and in red color? I also did not want the overlay itself to have any color (tint) on all the images in the gallery which happens when you use those caption settings in masonry gallery. It made all the images darker and I couldn’t find a way to control that.