If you study Neuro-Linguistic Programming, the Structure of Magic I & II, Milton Erickson, and Alfred Korzybski, it won't seem that magical.
Part of the trick is that during a routine operation - like a handshake - or asking for directions - you're brain drops down a level of awareness - you are basically on auto-pilot - but the illusionist interrupts the operation, you're still stuck in sub-optimal awareness pattern, and then you get manipulated in some fashion.
I interpreted that last video more as a status game, actually. The guy, immaculately dressed with a posh british accent, creates a status differential by talking fast and flawless, by touching her a lot. This makes it very unappealing for her to flat-out contradict him. She's just giving him socially acceptable answers.
It's not arbitrary touching. When he's asking her about something she's unsure of, he consistently touches her left shoulder. When he talks to her about something sure, he touches her right. Then he uses those same touches when he wants to make her unsure or a color, or feel sure that a color is the wrong one he says it is.
I don't know to what degree that actually works, but it's pretty interesting.
Also known as kinesthetic anchoring, the bread and butter of basic NLP. It's pretty controversial like the rest of the material and is probably utterly ineffective.
The fact that _he_ believes it is important which shoulder he touches produces enough an effect that one can be fooled into thinking the touches have the power instead of the belief.
