9 and 4 are rtelatively prime, so the {9/4} star, which is blue, is simple.

Inside the {9/4} star is a {9/3} star, which is colored green. 9/3 reduces to 3 by dividing top and bottom by 3, so the {9/3} star consists of 3 equilateral triangles. The three triangles are colored slightly different shades of green.

Inside the {9/3} star is a {9/2} star which is colored orange. Since 9 and 2 are relatively prime, this star is simple.

Inside the (9/2} star is a {9/1} star or regular nonagon which is yellow.