Your events look a little complicated so I've made a new event sheet with how I would do it and you can tell me if this is what you wanted to do or not.
I've made a new event sheet, if you want to use yours, just change back the event sheet that the layout uses.
I've tried to make what you described, you can drag the blocks into the den and when you press spacebar (the button wasn't working for me) they get destroyed and a new block appears with the combined tint values of the previous blocks.
Also, Construct 2 already has a system to save/load, just use the save or load actions: https://www.scirra.com/tutorials/526/ho ... -savegames