It's painted on with something called indelible ink, meaning it can't be removed easily.

它是用一种叫做不褪色墨水的东西涂上去的，着它不容被擦掉。

And you can see how this process generates very little runoff and produces a colorfast pigment without the use of any chemicals.

你可以看到个过程如何产生非常少的径流，并在不使用任何化学品的情况下生产出不褪色的颜料。