The coworker who ordered it said it was for his Mom, who has a dark blue coat with a purple lining. At first I was going to see if I could pair a purple yarn with a dark blue, but it just didn't look right. So I tried using a lighter shade of purple, and it still wasn't working. I did all this in the store, I didn't buy any of it :).
Finally I found Lion Brand Homespun Tudor and paired it with Homespun Colonial, which is a rich, dark blue, and it worked just right. What was so nice about Tudor was that blue and purple are interwoven throughout the white yarn. It turned out that I started the scarf using Tudor white/purple, which transitioned to white/blue just when I was about to start using Colonial. It makes it look as though the blue from the Colonial bled into the white of the Tudor:
And it picks us aspects of the purple from the lining in her jacket, without being overwhelming. The coworker liked it very much. I had never used Colonial before, but the color was so rich and beautiful that it made me want to make something for myself!