Purple
You stop a spoon from moving by tying it with thread that's purple. The spoon wouldn't stop moving around, so you had to use your favorite purple thread to make it stop. It's the strongest thread you have.
Imagine tying this spoon down with thread that's a color other than purple. Ah, the thread snaps. Darn, you better use your extra strong purple thread (the best color for strength!).
し
むらさき
None
You have to use all of your purple thread, and now you need more. You go into the back yard and call over your purple sheep (し).
Oh, did you think purple things were made with dye? No no, purple is a special color. You have to find unique purple sheep to make purple thread and clothes.