I know that feeling well, too. It looks like all the people I pass by are almost "muted" or phantom. And it feels like the world is all washed out and faded. I feel really cotton-headed and of course, all of this makes me panic that much more.
I remember one attack I had where I actually had to take some time and determine if things around me were real or not.
It is indeed, as you put it, a "weird" sensation.
I find now that when I start to get an attack, it's that sensation that I notice first. So, I just remind myself that everything is okay and I then search for reasons I feel that way: over-tired, stressed out, not drinking enough water, etc. I find often, that sensation comes on when my sinuses are plugged (therefore putting pressure on my face and giving me that cotton-headed feeling, which leads to that "unreality"). When I feel like that now, I take steps to try and reverse it: relaxation, drink some water, lay down if I'm tired (and can lay down at the time), etc. Soon, that weird feeling passes and all is good!
I think when we get worried about that sensation, that's when we get into that panic cycle. Remember: it's just a feeling and it will go away, we just have to wait it out. It can't hurt us and many people feel that way from time to time.
Hang in there...it DOES get easier to manage riding out that feeling and then eventually not paying much attention to it at all.