Thanks! I just cancelled my black order and re-ordered the gray. Looks like I could change the size, but not the color on an order. FYI, after buying the gray it showed me a photo of the black one. Overall, the process was pretty painless though. Looking forward to a gray shirt!
Yes. Look for your username in the top right corner of the T-shirt. It should be to the left of the word "logout" if you're logged in—or if you're not logged in, you'll see in the top right the option to do so. Clicking on your username brings up a profile with forms you can fill in. Second option from the bottom is called "topcolors". You'll need to look up the Hex code for the colour you want (for example http://www.colorhexa.com/ee33aa).
::starts swiping fingers on a printed page to zoom in the text:: Hey, what the heck is wrong with this thing?
That works if you haven't set a new topcolor. (Actually, even for people who have set a custom topcolor, many HN pages still display the default topcolor, so the point in the parent post is correct.)
Also, being able to set the topcolor takes some non-trivial amount of karma, so you would have to have been using the site for a while in its default look anyhow.
