The melody of Rainbow by Sia runs 362 notes across 49 bars, 3:13 long in D at 82 beats per minute. The tab sits low on the neck, mostly under the fourth fret, one note at a time — no chords to barre and no strumming pattern to keep up with. A piano backing track plays the chords and bass underneath, so the line you are learning sounds like the record even at half speed.
Prefer to strum and sing it instead? Rainbow chords and lyrics.