Rainbow is about these children who follow the whereabouts of a rainbow. One of the kids steals the rainbows gold (yes! The rainbows gold) and this causes color to drain from the world.

大体意思就是说几个孩子到了彩虹所在的地方，一个孩子偷了彩虹金子，这导致世界失去了颜色。

youdao

At first Nixon tried devaluation, but the amounts were far too small to stop the gold drain.

FORBES: Give The Gold Standard Its Due

This created a drain on our gold reserves, and if something were not done, it was likely that the U.S. would lose all of its reserves.

FORBES: Give The Gold Standard Its Due

Nowadays, India is by far the world's biggest buyer of gold and those imports are an increasing drain on an economy that is growing too slowly to reduce widespread poverty.

NPR: Baubles To Bars: India Gold Culture Defies Curbs