If you're in the UAE for more than 5 years, you will acquire a skill of identifying nationalities. You can't be in Dubai for 5 years and won't be able to tell nationality, seriously.
The only confusion you will have is the difference between Indian and Pakistani but they can tell. I mean, Indian will be able to tell if someone is Pakistani, or Bengali or Sri Lankan.
Europeans will be able to tell each country because it's their own region, they know their own and that they look different.
Just like how I can tell if someone is Chinese, Japanese, Korean, Indonesian, Malaysian, Thai, etc and not my own.
So, if an Arab see an Arab somewhere else they can tell -- Egyptian, Lebanese, Syrian, Kuwaiti, Bahraini, Saudi, etc even if they are not in their sheilas and abayas or wearing anything Arabs on them. It's their makeup, the features, the accessories, the colors, etc.
- Kuwaiti girls are more on their skin. If a Kuwaiti wears (or not) an abaya in Kuwait, she'll do the same outside her country because they have their freedom there so she'll be natural outside. They also love to accessorize and put colors, bright colors. Kuwaiti men love bling-bling.
- While Saudi girls are the opposite. Most likely they remove their abayas when they're outside their country. Also they put really nice and extra dark kohl over their eyes to bring it out because normally those are the only features visible to others in their country.
- Emirati girls have certain ways on putting their make up and more obsessed with blings. You'll find them blinging a lot.
What about you, can you spot the difference?