Conditional Formatting Based on Multiple Text Values

As you have a list of cities for each region just name those lists (right-click, define name), e.g. Region1, Region2 etc. Then you can use this formula in conditional formatting

=MATCH(C2,Region1,0)

add required format and repeat for the other 3 regions.

In that way you never have to change conditional formatting - if you want to change, add or delete cities just change the lists accordingly