It is easier if both your butterflies are the same color, then it only takes one large group of blocks to release them both.
Make the largest groups you can of one color block until the butterfly that color is released.
The game gets harder when more colors fall.
You can set off the line line blaster to try and get different colors, if the blocks do not match the butterflies.
But don't waste too many moves doing this, instead try to work with the colors you've got.
Use the paint to make more of the colors you need, and remember that larger groups work best, so don't try to release the butterflies unless you can click a large group or two in a short time span.