Apparently you can move the blue block with the red block (when you're red yourself) using your magnetic powers, but I also couldn't jump on the blue block to progress.
Running back and waiting for AI to turn for a minute each time to switch colors was also quite frustrating.
Viewing post in Color Hecatomb jam comments
(spoiler) you need to jump off from the ledge in the beginning to the top of the blue block.
I have just tested the game and found that if you get killed while you are grab mode ("telekinesis"), the block that you were grabbing becomes movable by other blocks until you grab that block again (which resets it's physics properly), will fix very soon. You basically found the only thing in the game I didn't intend for lol