Exercise all the yin and yang to get out of the fire pit, and stay innocent in the world. Where should this couplet be posted?

It is not "innocent", but "Qingbai" Qingbai is the yin and yang

It is posted in the brick and tile factory.

Yin-Yang refers to tiles. Yin-Yang tiles are green unglazed clay-fired tiles with a slightly curved cross-section. They are used as both bottom tiles and covering tiles.

Green and white refers to bricks, blue bricks and white walls. Green bricks are fired from clay, which is the product of long-term weathering of certain aluminosilicate minerals and is named after its extremely strong stickiness. The clay is mixed with water to make bricks, which are then calcined in a brick kiln (about 1000°C) to make bricks. Clay contains iron. When it is completely oxidized during the firing process, it will produce ferric oxide which is red, which is the most commonly used red brick. However, if water is added for cooling during the firing process, the iron in the clay will not be completely oxidized and low-priced iron will be produced. (FeO) is cyan, that is, blue brick.