Unfortunately, I wasn't able to get the CSS stylesheet to cooperate with me; nothing I tried to change the color of the subtitle-link font worked.
Using the twentyfourteen theme, the subtitle font size was fine on a desktop; however, it didn't scale on a mobile browser. On a mobile, the subtitle font ended up much larger than the original main title. That was the purpose of wanting to make the subtitle a link in the first place - because otherwise it seemed confusing to have the bigger font (the subtitle) not be the link.
But when I was able to get the subtitle to be a link in the same manner that the main title was, it changed the subtitle font color from black to green! Not at all what I was wanting!
Again, I wasn't able to get that taken care of in the stylesheet CSS. Probably because I'm not handy with coding.
I used the following code in place of the supplied code found in the FAQ/Installation Instructions:
<?php if( function_exists( 'the_subtitle' ) ) the_subtitle( '<h6 class="subtitle"><a href="' . esc_url( get_permalink() ) . '" rel="bookmark" style="color: rgb(0,0,0)"><font color="000000">', '</font></a></h6>' ); ?>
Obviously, if someone is following along, you'll want to change both color values (the style="color: rgb(x,x,x) & font color="XXXXXX") to the color of your choice. Black font is what I was wanting. And, yes, I took it down to an H6 from an H2. That was the compromise for the subtitle font not scaling down on a mobile browser. It still looks fine on a desktop - it just isn't as big. Which is fine for me. It still looks like a subtitle because of the placement and bolder font.
helgatheviking, if you'd be so kind as to look over the code to make sure I didn't mess anything up, I'd be grateful.