I think it's only scummy if it sets out to confuse users as to which site they are on. Changing both the font and the color scheme would seem to make that less

I think it's only scummy if it sets out to confuse users as to which site they are on. Changing both the font and the color scheme would seem to make that less likely. Otherwise, emulating decent look-and-feel is often a good thing: it is how we come to better designs and users with predictable expectations.