The definitive source of information about this scarf is, of course, The Doctor Who Scarf, a site put together by a fan. It includes a history of the scarf (and its various permutations), an exhaustive run down of which version appeared in what episode, detailed instructions, yarn suggestions, and more.
I chose the original version from seasons 12 through 14. I'm a fan of Brown Sheep Nature Spun from previous projects and like that it's 100% wool. I used sport weight. Note that the quantity estimates on the web site are generous: I have almost enough left over from the first scarf to make the second one I'm working on! I'll only have to order a few more skeins in specific colors.
Speaking of colors, here's what I used from the Nature Spun Sport line:
- Beige: Ash (720)
- Brown: Bev's Bear (N94)
- Yellow: Sunburst Gold (308)
- Green: Nervous Green (522)
- Purple: Plum Line (N18)
- Red: Red Fox (N46)
- Gray: Charcoal (880)
I ordered my yarn from Paradise Fibers, but Nature Spun is widely available online and brick-and-mortar.
The entire thing is done in garter stitch. Row after row after row of knitting... I highly recommend a row counter, and you will quickly get in the habit of double-checking those counts. Every color block is an even number of rows, so the color changes appear only on one side.
Oh, and I recommend you stop periodically and weave in your ends. You'll easily be changing colors over 50 times, so there's a lot of ends to deal with. Not only is it tedious to do that many ends in one go, all those loose strands get a bit messy to deal with as the scarf gets longer. As you can see below, I need to take some of my own advice.
The tassels are the last thing to add after casting off and before blocking. Make them longer than they should be - and include each of the seven colors - then trim carefully to neaten. I like using my rotary cutter with a straightedge, but some people find that "too" perfect for a handmade item and prefer to hand trim.
Blocking. Well. Lay out several towels end-to-end, doing your best to stay out of traffic areas. I actually have to stretch it from my dining room into my living room. Hope for low humidity so the monster dries fast.
Enjoy!