Brazil city is colored green (instead of grey)

General talk
1

The residential area of Anápolis in Brazil is rendered green: https://www.openstreetmap.org/way/458515620

Is this a rendering or a tagging mistake?

2

Yes, it looks like a tagging mistake:

https://www.openstreetmap.org/relation/3805357

3

The entire area is mapped as a park - hence the green rendering.

This is the park relation multipolygon:
https://www.openstreetmap.org/relation/3805357
And this is the outer way of this multipolygon:
https://www.openstreetmap.org/way/286850750

4

On Dec. 5th user Miduim changed a residential area relation encompassing the whole city into a park.

You might want to contact Miduim via that offending changeset what their intentions were.