How do I format the text and headers that relate to comments

I thought I was familiar with how the css style sheet and php pages work because I figured out how to get most everything else the way I want it in my custom theme, but I can’t seem to figure out how I can make the comments and the headers appear as I’d like them to.

I probably just need a nudge in the right direction.

Everything is fine on this dummy page until I get down to “2 Responses to….”

That line is an h3. I can change the font size, but I can’t change the color or anything else about it that I’ve tried.