Overlay in Supply

Site URL: http://www.furrylittlepeach.com/

Hi there,

I would like to achieve a gallery wall where each images title can be seen when hovering over the image.  Does anyone know how to do this where the overlay is transparent white, the caption is opaque and black, and the text is in the center of the image?  I provided a link to a website in Supply that already figured it out.

Thanks for any feedback.