Colored glow applied strictly over the horizontal axis. I'm not a vegas user so I wouldn't know exactly what to use within vegas for this. But it's very straight forward so I'm guessing other people should be able to tell you based on my description just now.
You can also duplicate the track, add Color corrector and horizontal axis blur to the top track. lower the opacity, and just mess around with it you'll get it.
The second video used a gaussian blur through channels green and blue but not red. A gaussian blur through green and red would have a blue tint... ect.