It's either tiny ice crystals in the clouds that act like a prism when the sun below the horizon hits them, or it's a mix of some chemicals.
Edit: I think you need a LIDAR machine to know exactly which one it is, but considering we are in the north, it's sub zero and we have pure air, I'd vote for ice crystals.
Sounds legit and certainly looks that way.
Hope you're having a good weekend. 🙂