Smells for me are sphere like with usually one color, but occasionally a gradient between two or three. But the big difference is the texture or peaks and valleys on the shape.
It isn't overlaid in my visual field, more like how you imaging or remember things in your head, very hard to describe. I usually don't pay attention but it is just there.
noteworthy? If I concentrate I can follow the trail of someone with a strong sent that had walked by in the last say 10 minutes like a blood hound. I _know_ when fish is labeled incorrectly when I do my weekly grocery shopping. I know when that person from work says they are quitting smoking, but have had a smoke and are lying. Just walking around outside, the amount of death from animals would surprise you.
Very specifically on the visually side I come across a food item that looks slightly different. No one else notices this change in smell but it is a fun game realizing that maybe the recipe changed ever so slightly or something.
Mostly I learned long ago to not talk about it in person because then people get very curious and then get extremely self conscious.
I don't have this in general, but when you were talking about someone who is quitting smoking I just realised that I have a distinct visual impression of the smell when a smoker really needs to have a smoke. It's kind of yellowish and it falls off them and gathers at their feet like a kind of fog.
I'm a super taster for a few things and I suspect that whatever odor that is, I can detect it better than most. Anyway, thanks for your description!
I have synesthesia and I 'see' sounds, but see is a misnomer. There is a visual component to audio but it's not a hallucination in my visual field. It's definitely in my mind's eye, but it is consistent which leads me to believe it's more than just imagination. Some sounds are definitely 'purple'.