Sorry but i dont have the reference photos that i take myself and i am afraid with copyright issue. You can search google “monas” to see the real building.
Just a quick question, do i need to make it as a seperate object if i want to color the top?
I can only put one color in the material
No! You can add many colors to a single object.
You don’t need to divide them into different objects.
Although it is sometimes better to make different parts, it’s called modular design.
Go to the material tab, add more materials (+), give them a color.
Then open your model in edit mode.
Select some of your faces, then select a material in the material panel and press assign.
You assign that face(s) to that particular material.