We also added themes (in the side menu) to address some of the feedback on contrast. Classic theme reverts to the color scheme of the old site. And you can fine tune the individual colors further in Settings.
I was about to post a link to Instinct . I've recommended your site to a couple of people after seeing it on HN when it launched, and both of them have loved it. Congratulations on building a great looking site with a novel approach to learning to play guitar from scratch!