Not much luck with the Gunsons Colortune

[His Dudeness]

I think your main problem is the spark plugs. They look old and fouled. I think it's time for new ones. In your video of the cylinder that was arcing, I'd guess the fouled plug is causing high resistance and the electricity is finding a lower resistance path through the colour tune to the head. When it does that you lose spark on that cylinder and you'd be running on three cylinders so to stop that I'd replace the spark plugs. Next I'd check that the air filter is in good condition. Next if you've been adjusting the mixture screws I'd set them back to what it says in the manual. After doing all that it should be running right and you can do some fine tuning with your colour tune.  The coils seems to be putting out a good spark so I wouldn't replace them.