@trevordeclercq, thanks again for your comments. Your voice and expertise is extremely valuable to us as we continue to improve Hookpad and Hooktheory.
To respond to your comments, it is true that Hookpad makes the assumption that diatonic scale degrees are in a sense, normative. Ultimately we must choose some reference, and we feel that the major scale is the preferred choice. As a consequence of this, chords such as ♭VII appear hashed; however, I disagree with you about the importance of ♭VII. We keep detailed statistics about the relative frequency of chords and scale degrees. ♭VII is actually far from a common chord among the 5000 songs currently in the Hooktheory database. The most common chords are all diatonic: I, IV, V, vi, ii, iii (although I agree that viio is not too useful), as are the scale degrees. ♭VII ranks 13th, and is far less popular than V6, which uses a natural 7 in as its bass. Scale degree 7 is over 50 times more likely to show up in a melody than ♭7. Of songs that do use ♭VII, many of them only contain I, IV, and ♭VII and have no instance of scale degree 7 in a natural sense, so many would argue that these chord progressions are properly mixolydian in nature.
The colors are important to us, because they provide an additional dimension in which harmony can be visualized. And while everybody looks at a theoryTab differently, many of our users (especially those who don’t know any other system) rely on the colors to orient themselves to the scale.
However, as you point out, if we use Method 1 (outlined in my previous post) the colors and labels in the “popular” style notation could serve a dual purpose; they would simultaneously show the cyclic nature of the scale (la-based approach) while also showing the relationship to the parallel major scale (do-based approach). While there are still a downside, I think that ultimately this color-scheme may be the best option if we were to implement this notation style.
Regarding the Ionian/Major issue, I suppose it is understood in modern music parlance that when we speak of modes, we’re speaking about modes of the major scale unless otherwise specified. Please correct me if I’m wrong 