Start working on CAD, mainly illustrator

I wanted my collection to have modern look to it, so for that reason I decided to work from a collection  of modern architecture buildings.
I started by taking the images on to illustrator and take outline drawings of these building so I can use them to built my design with. The important thing that I had to do when drawing the outline was, I needed to separate every layer so each section of that building can be use on its own and to make the job essayer for myself I chose different colour for each layer that I drew, as you can see the outline shape of each building has different colours to it.