The figures were painted in black pigment on the natural red clay ground. finishing details were then incised into the black pigment revealing the red ground.

用黑色颜料将图案描绘在天然红色的黏土坯体上，到修整时再在黑色图案中刻画细部，露出红色的坯体。

youdao

The clay figures, 8, 000 in all, were actual likenesses of Qin's army, cloned in clay to guard him in death as his real soldiers had in life.

CNN: ASIANOW - TIME Asia | Visions of China: Xi'an