O is for Opalescent
Opalescent: exhibiting a play of colors like that of the opal.
…
Mai was always pretty to look at, Yasu thought, under any given moment. She was always shining with a pure, iridescent light. The color just depended on the mood she was currently in.
When she was in deep thought about something, she had a deep, white glow to her. When she was in one of her lovesick moments, she was decked out in rich red and feminine purple. And when she was ecstatic, she was an array of beautiful colors. When she was sad, she looked mournful in gray and blue.
But whatever color she was, she was always pretty.