Have you had any luck with more progress? I am stuck around e55 as well. I also noticed that it says you need to get 10 rows of green to unlock supernova 2. Based on what I have seen so far, if something else is not unlocked after reaching green, I am afraid it might not even be possible to progress at all
My best progress has been rerolling for as many 9s as possible to get around e43 blues before switching to cubes but yeah it becomes untenable toward the middle of the last row. You end up needing to roll basically all 9s (or at least no 4s or 3s) to make a dent in progression. I haven't made it to the e56s, I couldn't afford that much micro so I've fallen off. I was really hoping to get a green square :(