It looks like this is what you already have created. The zip codes are not connected in any way, so each zip code will be colored individually based on the region it belongs to. This is why you see filled colors of red and green in various areas (yellow only applies to one zip code, so its very tiny and difficult to locate without using the 'Hightlight Selected..' option in the legend. So, I'm not sure I understand what you are wanting to do?
What i want is to show one single color for the zip codes belonging to a region as opposed to showing them as spots on the map.
Yes, I understand--but how are you expecting to do this with the data you have? The regions are not inter-connected, and the zip codes are all over the place. What you already have is basically a filled map showing the zip codes, colored by region. I'd be interested in seeing a mockup of what you expect to produce in Tableau.