Changing size & appearance of "leave a reply" in TwentyTwelve

This is a cosmetic thing only: Is there any way to change the size of the “Leave a Reply” text? I’ve been searching for the text itself and cannot find it, but have been looking around the content.php file which is where I thought it should be. (I use a child theme and edited content.php a while back to move “Leave a Reply” to the bottom of my posts, but changing the size and color of the font has me boggled.)

Alternately, if there is a plug-in I can use to change the reply to a button or something similar, that would be fine, too.

Thanks!

URL: shebloggedbynight.com
using Twentytwelve with a child theme