I've not experienced a problem like this myself, but the fact the asker is trying to stop and finding it difficult does remind me of a surprising but well-established finding in psychology that the harder you try consciously to not to think about something, the more you end up thinking about it and the bigger a deal it becomes. I think this is part of the problem, and could explain why the asker is finding it harder to get over it than Ray did.
The classic experimental example is: if you tell half a group of people to imagine a polar bear (white bear), and half to not imagine a polar bear, the group consciously trying to not imagine the bear have the image of that bear closer to mind than the people who are imagining it. They recognise white bears faster than the other group, and they're more distracted by pictures of white bears than the other group.
It makes sense when you think about the effort involved in enforcing a mental taboo like this. You have to maintain a really strong representation of the thing you're supposed to not think about, so that you can check your thoughts against it.
It's likely that the harder the asker tries to not to notice his colleagues' dress, the more he notices it.
How to deal with this? I think this reinforces an important subtle detail in Ray's answer. Ray didn't get over this problem by trying consciously to not notice it any more - he got over it by focussing on other things like work objectives, (slowly) relaxing and just getting used to the fact that in this context, it's normal. Then he no longer noticed it.
Consciously fighting it will just lead to you thinking about it more, worrying about it more, fearing it more and as a result, noticing it more.
Humans are probably the most adaptable species on earth. We're very good at getting used to shifting norms - except for when we fixate on something and complicate it.
Let your brain do what it's good at, without getting in its way, and like for Ray, it'll quickly stop being distracting.
I've never had a specific problem like this, but we've all ended up in a situation where trying not to notice something you're supposed to ignore at the workplace has led to becoming awkwardly unable to think about anything else - and where the harder we fight it, the worse it gets. Some more common examples:
- Trying to ignore a colleague's quirky habit, catch phrase or laugh that only you find annoying
- Trying not to think about that scandalous rumour you heard about a colleague while discussing business with them
- Trying not to notice a distracting blemish, spot, nose hair, bogey, stain, undone fly, obvious wig, mismatched socks, shirt tucked into underwear, unexpected tattoo, curious scar, etc etc while someone is giving an important talk
All these things get worse the more you fight them and the more you let them get to you.
I think the asker is basically experiencing this, but on an epic scale, all day, every day.
It won't stop until they relax, stop worrying, fighting and fearing it, and let their attention get taken by more important things until they get used to it.
You don't stop noticing a speaker's unusual accent by thinking "I must stop noticing this speaker's unusual accent". You stop it by thinking "This speaker's talking about [x]. That's relevant to my work" and keeping focus on the matter at hand. Same for any source of distraction.
If it's also hard to stop thinking about it because you're genuinely convinced their dress is "seductive", it might help to resolve this cultural misunderstanding:
- The intentions certainly aren't seductive. Most people (male and female) avoid starting relationships or liasons in the workplace. They get very awkward very quickly. People (male and female) put effort into looking good at work because it's expected that ambitious professionals will "make an effort" to "create a good impression", by dressing smartly and reasonably fashionably.
- It's possible one detail you're not used to is tight outfits that show the wearer's body shape. In Western business-wear, for both men and women, an exact fit is considered smart, and bagginess is considered sloppy. The ultimate in smartness is a tailored suit (or a dress) that perfectly fits your exact measurements. If someone wears an outfit that is a very sharp fit, it's not their body shape they're showing off, but rather it's about professional qualities like smartness, neatness, precision, control.
- People also want to feel comfortable - and this also includes feeling like whatever level of femininity or masculinity the person is most comfortable at. Maybe the details you find distracting are actually just flourishes chosen to make a smart but bland outfit feel more feminine.
And please please please don't do what some people have suggested, which is to avoid talking to or working with the people you personally find distracting.
First, it's unfair on them, and unfair on your employers, if you're not communicating with relevant or important people to your projects for personal reasons.
Second, for any personal problem, hiding from it or bottling it up lets it fester and feel so, so, so much worse than it needs to be.
You're a professional. You can get your focus back on the job when, say, hunger or tedium distract you, and you can get your focus back when other curiosities (like interesting SE questions) distract you. You can do the same with this, too.