In SimCity Buildit I am trying to upgrade my Premium Residential zones to Luxury zones. Will building a swimming pool do that?
A swimming pool might help increase the land value of the residential zones. The standard, premium and luxury types of houses are based on the land value. The darker the blue, the higher the land value. Adding more specialisation buildings will help increase the land value.
You can read more on EA's help pages: Building Residential Zones in Simcity Buildit