Its futile trying to exercise an opinion on this thread because of the company ringers like jdrtravel that trash every opinion that doesnt coincide with their agenda.
Navy blue is, as you say, worn by 90% of airlines because it is considered a business professional color, similar to black and charcoal grey. IF you have ever spent any time in a professional business environment you would know that. That is why the blue blazer is a staple wear for professios. Purple, on the other hand, is NOT considered a business professional color.
In my insignificant opinion to the online ringers, appearing professional is much much more important than appearing distinct. That is the reason why pilots of most world airlines dress in a similar fashion.