So the 1.13 patch introduced purple water, but who needs purple water? My sims needed this.
Thecontains three separate packages; green, murky, and yellow water (yes that is water! I promise!). Found in the new Pool Water section (Build Mode > Pools, see screenshots) for 12§ (yellow) / 32§ (murky) / 52§ (green).
See this post (mts Create > Tutorials) for how to make this.