Make her eyes rainbow, and what do you want to discuss about her cutie mark
Also, here's the description for the second OC
Design: Mane and tail are composed of galaxies(not literally, despite her being 10 times the size of a Ursa Major), and is shimmering. Coat is composed of many different colors. Ocean-blue, forest green, sky-blue, fiery yellow, orange, and red, dirt-brown, cloud-white, stone grey, and containing multicolored dots for flowers(all of which is sparkling). Her eyes are golden and are swirling and sparking like a cosmic storm. And her magic field constantly changes between many different colors
Her wings shine like 100 suns, bringing light to even the darkest places, and making night seem like day.
On her head is a crown with a rainbow in front and 18 miniature stars hovering slightly above golden crystals, with a base formed from clouds.
She has no cutie mark, for she doesn't need one. Why have a cutie mark, when you're at the top.