I'm okay with anybody who wants to create additional spells based on me. (I didn't actually give explicit permission for the first spell, but whatever. It's okay.)
I intended this be a level 7 spell, but I think it turned out too strong for that.
Gfishfunk's Prismatic Wave
8th level conjuration
Casting Time: 1 Action
Range: 120 feet
Components: V, S, M (A drop of water)
You conjure a multicolored tidal wave that covers an area in range. The area can up up to 35 ft long, 15 ft wide, and 15 ft tall. Each creature in the area must make a Dexterity saving throw. Creatures in the area take 4d8 bludgeoning damage and are knocked prone on a failed save. They half as much damage and aren't knocked prone on a successful one.
Each creature in the area rolls a d8 to determine what color of the wave affects them further.
1. Red. 5d6 fire damage on a failed save, half as much on a successful one. Being underwater does not grant resistance to this fire damage.
2. Orange. 5d6 acid damage on a failed save, half as much on a successful one.
3. Yellow. 5d6 lightning damage on a failed save, half as much on a successful one.
4. Green. 5d6 poison damage on a failed save, half as much on a successful one.
5. Blue. 5d6 cold damage on a failed save, half as much on a successful one.
6. Indigo. On a failed save, ice forms around the creature and restrains it. It may make on a Strength saving throw at the end of each of its turns in order to try to escape. If it saves twice, takes 15 or more bludgeoning or fire damage in a single hit, or a minute passes, the ice shatters or melts, and the effect ends. The successes don't need to be consecutive in order for them to allow a creature to escape.
7. Violet. On a failed save, violet ink covers the target's eyes, blinding it. It may make a Constitution saving throw on the end of each of its turns in order to end this effect. The ink clears out after five rounds.
8. Special. Two splashes of color affect the target. Roll twice more, rerolling additional 8s.
The water then spreads across the ground in all directions, extinguishing unprotected and flames within its area and within 30 feet of it. The water is normal water after the spell's effect, except for its unusual color.