Because, I borrowed a bit from Heroes of Beacon. Also, in RWBY lore, most characters co correspond to a color or set of colors of some sort. In this way, players can be aware of what color or colors they stand in for. This is also usually indicated in the name of the character in some fashion, or is thematic in nature.
For instance, Salvia, is the general family name for types of sage plants. Weiss, means White in German, which means Sage White, or.. specifically White Sage. Sage, is also a term for someone of great wisdom, knowledge, or connection with nature. White Sage is also used in purification rituals, induction of positive energy, and change or reform. As such, this is all an interconnected play on each other.
Yin, the golden girl, is actually a reference to Goldilocks. Ruby Rose has multiple references to color in her name, as well a the rose that is on her person. She is also an allusion to Red Riding Hood. Wiess from the series is a reference to Snow White, as well as Weiss being "White" in German, like I mentioned a minute ago. There are also similar references to Blake and Black. Cinder, one of the bad guys (bad girls in this case) is a reference to Cinderella, and so on.