It's plain to see that this is a stocking stitch scarf, probably a tube scarf. It looks like the scarf is pretty wide, and the stripes are not as tall as they are wide. So if you are making your scarf 6" wide, make the stripes about 4" tall to keep it in proportion. There is also fringe in alternating color bunches, about the length of a color stripe. I'm estimating the length of this scarf as pretty long, because you can see that Hermione has hers tied around her neck loosely, and it still reaches to about her waist.
There has been some discussion online about whether these scarves are the wrong colors. People are saying that they are "maroon and yellow" when Gryffindor's colors are "scarlet and gold." I'd like to point out the difference in color values even between the above photos, which were all taken of the same scarves. Everyone must keep in mind that different screens display colors differently, and so do different media types! Make the scarf the color you think it should be, don't try to match what you see on your screen, because when you see on the big screen, and when you get it on video and watch it on the little screen, you're sure to see a different color!
These are my takes on scarlet vs. maroon:
I think everyone's making way too big a deal about this. Pick the color you want and tell yourself that it's the right color for you! Or better yet, let the person you're making the scarf for pick it, so they won't be able to complain. =) I used "burgundy" and "gold" Red Heart yarn, as per my boyfriends' requests. Burgundy is closer to maroon than to scarlet, but Matt did not like the scarlet that was available in RH.
Something else to think about: scarlet and gold are the colors for Gryffindor House, so you could easily use the colors from another house if you wanted to represent those houses instead. Those colors would be:
Ravenclaw: Blue and Bronze
Hufflepuff: Yellow and Black
Slytherin: Green and Silver
Note to knitters: These scarves are NEVER mentioned in the books. They are a new thing made for the movie. So if you want to make something more authentic, you might prefer to make Dobby socks (mismatched socks in crazy patterns) or a scarlet sweater with a gold lion on it, which Mrs. Weasley gives to Harry for a Christmas present in the third book.
Update 10/30/01: I found a picture online, drawn by the original illustrator for the HP series, and it shows Harry wearing a striped scarf, standing in front of the Hogwarts Express! So there IS a reason for the scarf's existence! It still isn't mentioned in the book, but at least we know it was not made up for the movie version! That makes me happy! (in case you couldn't tell!) BUT! This picture seems to support the idea that the colors in the movie are wrong, the red in his scarf would never be called maroon, though it is certainly not what I would call scarlet. Oh well!
Here is the picture (copyright Thomas Taylor):
Update 11/28/01: After watching the movie, I have a different take on these scarves. They are DEFINITELY tube scarves. They are also much MUCH wider than we had previously thought, probably at LEAST 12" across. The students receive these scarves the first night when they arrive at school, and in the movie you can see the scarves laying over the backs of chairs -- the scarves take up most of the chair backs! That is how wide they are when they are flat.
Update 12/11/01: The last 2 pictures I've added came from eBay, where several people are selling official scarves that were given out to press and others at the movie premiere. You can see exactly what the tassels are supposed to look like, and how the stripes look. I think these are the most helpful pictures so far!