I didn't style that part, but to change the font color of the comments themselves, you need to take .comment-content from it's current location, which is here:

.trackbacks-info,
.trackback-content,
.comment-content,
.comments-open-content,
.comments-open-footer,
.comments-closed,
.archive-content

And then you need to put in the following codes to style it yourself:

.comment-content { 
	color: #ffffff;
	margin: 10px;
}

The hex code I put it is for white, so you can go from there.