Borders…white to black

Hi.

I’m using the Cute Bubbles Theme and the author’s contact page was ineffective, so I couldn’t go to the source to answer this question. I’m very new to WordPress and themes in general, so I hope this isn’t a dumb question.

The images I’ve put into my pages are surrounded by a white border. This is jarring against the dark background, but worse, the default font color is white, so the captions aren’t showing up. I can’t find any way in the regular page/image composer to adjust either one, border or caption color.

The Theme Acid Rain is very similar except it has black borders around the images, with a nice light edging, and the default white lettering shows up fine.

Can someone tell me where this control code resides and what code I could use to change it to be more like acid rain?

Thanks.