I just realized my conlang has two separate ways of asking "why."
"Kian ńi ksa." = "The fish is red."
"Zei tsai kian ńi ksa?" = "Why is the fish red?"
"Kian ńi ksa mu zei?" = "Why is the fish red?"
The difference is that "zei tsai" is used to ask about causation, while "mu zei" is about purpose.