what is the dress code we have to follow to be identified as Hindu in foreign country
The poster had asked the question appropriately in the right thread 'Philosophy and Traditions'. So, I pre-sume, he meant about following such a tradition in a temple or hindu gathering or at home.
But, the 'need of identification' is still a question!
One may see, recently, that muslims simply resort to prayers publicly in foreign countries, simply to attract crowds. Whereas, sikhs follow turban as a custom.
Hinduism itself, is not meant to be followed for other's appreciation or for publicity or proselytizing. It advocates worship, prayer, adherence of rituals only to discipline one's mind regarding hygiene, self-control and realization. So, Hinduism has to be first understood and then followed, which would then ensue better results.
Why should a Hindu need a right attire for Worship?
The basic need for a clear mind is a healthy body [not the kind of Six-pack], but the kind of well oxygenated, well hydrated, alkaline (pH) gut. Such healthy body comes from the Sattvic practices - Sandhya -vandhanam/Yoga/Breathing [oxygenation] , then consuming sAttvic foods that can only be offered to the deities, avoiding those stupid entertainments [anything non-spiritual - violence/romance/vulgarity of words-actions - will only cause stress would upset the gut/body/mind], later devoting time on philosophical wisdom/ productive knowledge [-even science/critical-thinking/math/spiritual-re-juvenating arts-crafts are o.k. not the stupid Hussain kind], and end of the day, contemplating on one's self [self-awareness - like 'I was angry'] on those qualities that one need to focuss/correct the next day/next moment actively [meta self-awareness - 'I am going to be angry now, let me distract/control myself']. Thus such-awareness will develop with good body/mind and more live self-correction.
So, while following all these daily activities (nithya-karma), one should wear the right dress and the forehead marks, to ensure better assimilation of spiritual knowledge (lessons) from the daily practices.
But, freaking ourselves out in food habits, past-times, activities/karman, but wearing some outwardly traditional attires is like the muslim praying out on the streets. One should have the free-will to wear make-ups, face-masks and creams, but failing equally to eat nutrient rich - veggies and fruits [freaking out on their love foods - fried, acidic, fatty foods] is Self-Deception!!! This is exactly how every religion or faith is boasting to follow, without trying to correct their body/Mind and understand their Self.
Let us start following our external traditions in unison with inner realization/understanding, atleast one by one.