To start learning 周杰倫 - 彩虹 chords, build your understanding on these basic chords - E, Am, C, G, C, Dm, C, F and G in sequence. To build a solid grasp, start slowly at 74 BPM and then match the original tempo of 148 BPM. Adjust the capo based on your vocal range and chord preference, keeping the song's key of G Major in mind.