I presume we are talking about the bright scarlet red jackets, pants, and skirts.
This choice of color was obviously designed to attract attention to passenger trains, whose presence on one's radar screen was non-existant, or, was perceived to be an awful choice of a means of transportation. As well, red has always been used as a positive attention getter, so by using it on one's dress ware, it spoke to the public that we (Amtrak) are doing something to improve the broken down trains and railroad track; we are making trains a happy place to be.
Perhaps now is a good time to reissue an updated red uniform (crimson, maybe?) until Amtrak gets its house in order, whenever that will be.
And I can't agree more about the grey Acela: it gave the staff a cold, armed forces kind of feel. Ultimately, go with sharp navy outer wear with deep blue or white shirts and blouses, and use red accents for the ties, scarves or ascots, as well as, maybe, the lapels. Plus, the growing practice of letting conductors reveal tatoos ought to be a no-no.