Chromatic Corona

You create a circle of light around you from prismatic energy, once per turn, you can use your bonus action to add a ray of light to the corona, up to 9 over the next 9 rounds. on round 10 you use your action to fire all of the beams, selecting a target for each one and making a ranged spell attack against them, they can be directed at the same target, or multiple targets. You can use your action to release the spell early and fire all of the beams you have prepared, but if your concentration is broken, the circle shatters and the spell ends without using its effect. Each beam does 2d10+your spellcasting modifier  damage of a type based on its color, and you choose its color when you fire it. 

Red: Fire, Orange: Acid, Yellow:lightning, Green:poison, Blue:cold, Indigo:Thunder, Violet:Psychic 

For each level of spell slot it is cast above 3rd, it gains 1d8 of the selected damage type.