Sometime in the future, thread of every color will be faced with extinction. Eventually there will be nothing else to make thread out of, and thread of every kind and color will reach extinction.
The extinction of thread was brought on by a very strange thing. Deadly zits (ぜつ). These zits killed off all the producers of thread, and eventually the thread went extinct. Dang zits.
Currently there are no similar looking kanji which exist in the WaniKani learning system