Nintendo recently released even more details about the upcoming trilogy of Legend of Zelda Game Boy games. Already, Nintendo has released information regarding the first in the series, the Chapter of Power. The Chapter of Power has a theme of "seasons".
The second game in the series is the Chapter of Wisdom. It's theme is "color". Each event and puzzle has a relation to color in some shape. The final chapter is the Chapter of Courage. This chapter focuses on the theme of "time". The puzzles all focus on time, and many are unable to be solved outside of a specific time of day.
Additionally, Nintendo released details regarding a new group of people, known as the Ulra tribe. They come from the continent Ulra, inside the core of a volcano, and are blacksmiths. Further deatails are likely as the release of the Chapter of Power draws nearer.