Gallery image - overlay?

Site URL: https://www.birdmafia.com/gallery

All,

I'm not positive what I'm showing is called an overlay, but that's my best guess.  On this webpage you can click on any of the first 5 gallery images and see it. I want to change color of text and the overlay itself, but can't seem to find any of those settings in Design->Site Styles.  Maybe this template family (Skye) does not allow one to mess with it without CSS code? 

Any ideas would be appreciated. Can barely read the text as it's black on a close to black background.

Add to Home > Design > Custom CSS

/* Overlay background */
.yui3-lightbox2 .sqs-lightbox-meta {
    background: red !important;
}
/* heading */
.yui3-lightbox2 .sqs-lightbox-meta h1 {
    color: green;
}
/* description */
.yui3-lightbox2 .sqs-lightbox-meta p {
    color: green;
}

This works great, thank you!