Why does a secondary rainbow have its colours in the reverse order?

A secondary rainbow has its colours in reverse order compared to the primary rainbow because of the number of internal reflections the light undergoes within the raindrops.12

While the primary bow is formed by light that undergoes a single internal reflection, a secondary rainbow is produced by light that undergoes two internal reflections. This additional reflection causes the light to exit the raindrop at a different angle, resulting in the secondary bow appearing outside the primary arc with its colour sequence reversed. Specifically, the primary bow typically displays colours from violet on the inside to red on the outside, whereas the secondary bow reverses this sequence. Because this process involves more reflections, the secondary rainbow is also significantly less intense than the primary one.12