Rik, you are 85% there.
Before I do the big reveal, you are aware that when you change one blob's colour, then the End position control simply clones that blob.
For the image you have here, you can make red blobs and blue blobs but green blobs would have to be by hand.
As you have discovered the Page & Layer gallery is the clever part.
Select a blob there and then change the Tool to the Shape Tool and experiment.
Also with the Selector Tool, what can you do with the controls and meta-keys?
Acorn
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