Interesting how it can be different from person to person, mine looks nothing like that. For me it is not colourful, the border feels more like gray TV static than the rainbow in the video. Or sometimes it feels like a black and white stripe pattern, or sort of zigzag stripes that flash between black and white.
I should say, to get the real effect of what it looks like, keep your eyes pointed at the center of the screen (the shimmers are often in your peripheral vision and you can’t look directly at them)
I never heard of it when it happened to me for the first time so I nearly freaked out as I thought I was having a stroke.