While it’s not news that blue coat was fashionable among young men of Austen’s era, not everyone might be aware that it was due to Goethe’s influence.
In The Sorrows of Young Werther we read:
It cost me much to part with the blue coat which I wore the first time I danced with Charlotte. But I could not possibly wear it any longer. But I have ordered a new one, precisely similar, even to the collar and sleeves, as well as a new waistcoat and pantaloons.
But it does not produce the same effect upon me. I know not how it is, but I hope in time I shall like it better.