I don’t visit Twitter’s website regularly. I use Twitter from third party applications most of the time. Not sure when Twitter has another new look — the homepage has been changed few times — but when I open Twitter’s homepage, I got some different schemes.
Anyway, you probably remember about its major design few months ago. Now, Twitter randomize its homepage by having different color schemes. Not sure how many combinations it has, I found three. All of them give a short description: “Find out what’s happening, right now, with the people and organizations you care about.”