For hollow 2 color tubes I cut the body off just above the skirt with a razor blade and then re-inject the body. It's been my experience that (like with laminates) you get a much better weld if you do that as soon as possible vs. after the plastic cools/cures.
If your not super fussy about it...you can make two color (tail/body) "tubes" by making the body solid (there's a thread about this..but basically go buy a small bolt that fits the thread pattern so you have no insert going up the body to make it hollow) and then trading bodies and tails across the two colors of baits you have. For example...shoot a bunch of black ones and blue ones and then cut the tails off of both slightly above the tendrils and use on the opposite color bait.
You "weld" the body to the tail using the method that Frank shows in his video. After you get the hang of sliding both sides across the blade you can get really nice looking baits.
http://www.caneycreekmolds.net/index.php?topic=660.msg3293#msg3293 I've never been very successful with super glue..but some say it works for them.
I make about 25% of my "tubes" solid...because I like using the mushroom/half moon head jigs ...and I can switch color baits really fast this way. If you like to Texas rig your tubes then solid is the way to go!
Now...when you really want to get fancy....make your tails a solid color ...and then use a dual injector for a laminate body of two other colors! You probably won't catch more fishing with these...but you look really cool doing it!