You can only get this while using the flowers with the separate color inside. To define what it is looking for...it wants you to create 1 set of 3...that set then has at least 1 flower that changes color creating a 2nd set of 3 flowers...THAT 2nd set of 3 has at least 1 flower that changes colors and creates the 3rd set of flowers.
The best way to do this is create a sort of 'Z' shape except the up/down will make a straight line. There are MULTIPLE ways to complete this, and you will most likely get it just through playing smart aka "planning ahead" and putting like colors around your flowers based on the inside and outside color.. They called it "Plan Ahead" for a reason.
If you can get your 1st level to include a "PLUS" of 6 flowers, you will also get this: