Here is what the dictionary says about 青: 1. 深绿色或浅蓝色：～草。～苔。 Dark Blue or light green. 2. 靛蓝色：靛～。～紫。 Indigo blue. 3. 黑色：～布。～衣。 Black. Similar case is 苍: 1. 深青色，深绿色：～翠。～天。 Dark ...
There are a lot of different words for many concepts in classical Chinese, for instance for the personal pronouns. Due to which circumstances could this happen?