To release butterflies and save the Pets in this level you need to build up the paint booster 4 times to get the final pets.
This will enable you to make, then remove, at least 16 blocks the same color as the butterflies, which will release the butterflies so they can save the Pets.
There are 2 main obstacles to you doing this...
First, you need enough large groups of blocks to build up the boosters.
And second, you have to have the correct color blocks drop and be freed from mesh to use the paint on.
While you are doing this you'll probably also get enough blocks to release one, or both of the butterflies that are under the outer Pets, but this is not essential as there are enough butterflies to save them all at once.
It is better to save all the correct colored blocks until your 3rd or 4th paintbrush, as if you do not click all 16 blocks within a short amount of time the butterflies will power down and need even more blocks to get them moving!