supernumerary rainbow
A faint, extra set of rainbow bands inside the primary bow, caused by diffraction of light by small water droplets. Technical term in meteorology.
A supernumerary rainbow is a faint band of colors seen inside the primary rainbow.
Compound of 過剰 (excess, supernumerary) and 虹 (rainbow). The term is a direct translation of the English 'supernumerary rainbow'.