1. Remove these two blocks. Be quick by pressing the THRUST key (shift, space or ctrl). The pumpkin must move to the left when you release it. Remove the left blue block so that the second ladybug gets caught in a circle path around one blue block (see next image).
2. The first bug will destroy a cactus on the left side if you've done everything right. The second ladybug should walk in a circle around one blue block. Remove this block while the bug walks up so that he will wander to the right and destroy one cactus there.
3. Now you've got access to the blue blocks and to the red color switch.