Withmore City exists in a giant, mirror-like glass dome. According to the wiki, the diameter of the initial build is 17 miles wide, which is the distance from an end of the dome to the exact opposite end. For the sake of simplicity, and based on currently available illustrations, we will assume the dome is a hemisphere, e.g. a spherical shaped dome, so the dome is also 8.5 miles tall.
Withmore is divided in four levels, Red, Gold, Green, and Blue. That means we can assume each level is 2.125 miles apart, or these miles tall (if they are evenly divided, which seems like the most logical approach from a structural point of view).
Using this tool (https://www.monolithic.org/calculators/dome-calculator) we can calculate the radius of each level of the Dome (remember the radius is half of the diameter. So in Red, its diameter is 17 miles, in Gold it's 16.46 miles, and so on).
Level 0 (Red, 0 miles above sea level): 8.5 miles
Level 1 (Gold, 2.125 miles above sea level): 8.23 miles
Level 2 (Green, 4.25 miles above sea level): 7.36 miles
Level 3 (Blue, 6.375 miles above sea level): 5.62 miles
We can picture each level being a "layer" in a cake, where each layer is smaller than the previous one as they go up, due to the spherical shape of the dome. Using the classic formula (A = PI * (d/2)^2) we can calculate the area in miles for each sector, based on the radius we've just calculated.
Level 0 (Red, 8.5 mile radius): 226.980 square miles (roughly the size of Chicago, IL)
Level 1 (Gold, 8.23 mile radius): 212.789 square miles (roughly the size of Columbus, GA)
Level 2 (Green, 7.36 mile radius): 170.1788 square miles (roughly the size of Tampa, FL)
Level 3 (Blue, 5.62 mile radius): 99.2235 square miles (roughly the size of Milwaukee, WI)
This aspect has the most variables because it's hard to reach a consensus of how many people live in Withmore City's various sectors. We know the base population is around 75 million people. Not to mention that there are no residential buildings in Gold, so its population is highly transactional. However, after discussion with some staff and members, I am proposing the following ballpark numbers:
Red: 50 million inhabitants. Pretty much everyone lives here, and it's the focal point of immigration.
Gold: 14 million inhabitants. As people come and go to work from Green and to Gold, Gold has at least ten million people in it at any given time. Consider a few more Mixers which go to Gold for banking and cloning.
Green: 10 million inhabitants. If you work for a corporation you live here. Assuming people go to Gold to work and come back to Green to sleep both for day and night shifts it makes sense to have the same amount of people in Green as there are in Gold.
Blue: 1 million inhabitants. Let's say 1% of the population lives in Blue. The percentage may be even smaller, but at 1%, we have 0.75 million, rounding it to 1 million.
This is the easiest part of our calculation. Simply divide the area by the amount of inhabitants and you have an amount of inhabitants per square mile, which can be compared to readily available data online. As of 2019 the most dense city in the world is Manila, Philippines, with a density of 107,561/sqmi, of 1,652,171 inhabitants for an area of 16.55 sqmi. We can also compare it to New York City, in NY, with a population density of 27,016.3/sqmi, according to Wikipedia.
Red: 220,283.725/sqmi (2.04 times the density of Manila and 8.15 times the density of NYC)
Gold: 65,792.874/sqmi (0.6 times the density of Manila and 2.43 times the density of NYC)
Green: 58,761.725/sqmi (0.54 times the density of Manila and 2.17 times the density of NYC)
Blue: 10,078/sqmi (0.09 times the density of Manila and 0.37 times the density of NYC)
In 2019, Red would be the most dense city in the world, double the density of the most dense city in the world.
Gold would be a sprawling business center, with extremely dense population of pedestrians and vehicles in the streets, like Manhattan on steroids.
Green would also be dense, parks sprawling with people and children, a suburb with heavy traffic.
And Blue would be a sparsely populated, albeit immensely wealthy suburb, where only the rich are allowed to live.