A guaranteed place to obtain this is in the mission Board Conspiracy during chapter 3. You start next to a blue geo block. Throw it onto a red spot nearby and destroy it. This will give you exactly five color changes.
Note: this must be done on your first time in the stage as the you cannot return to this level with this configuration.
If you missed it on this stage you'll have to find a suitable level in an item world and toss around blocks until you can achieve it, but it is much more time consuming. It's that or start a new game.