Multiple Master pages with multiple columns

Hi

I have a document which I need to place in Indesign.

My requriement is as follows:

Letter Size / Landscape Pages

One master page required for Chapter Opener which will contain a graphic element and Main Heading.

I have attached a screenshot.

5 master pages are requried for Body Text becasue body text will flow as follows:
a. Some pages will be 2 columns. Basic Body Text with 2 Cols.
b. Some pages will be 3 columns. Basic Body tex with 3 cols.
c. Some pages will be 2 columns with First columns as a rectangle filled with color.
d. Some pages will be 3 columns with a graphic image running from left to right like banner.
e. Some pages will be 2 columns with a graphic image running from left to right like banner.

I have made few master pages. I have attached screenshots.

I placed the text using Basic Body Text with 2 cols. All the pages where placed.
Then I dragged the master page with first Cols as Blue Box and other 2 cols as body text.
The Blue Box came, however, the the text did not change to 3 columns. For some reason it aint working.

Need help urgently. Stuck with a new projet. Thanks.