I was looking at the matoran language and found these three matoran prefixes for these three elements; Zov for Solar Energy, Iki for Acid, and Mag for Lava. So here’s the matoran I came up with them by and also maybe even for the Toa they become.
Zov-Matoran(Solar Matoran)
Colors:silver and white
Zov-Matoran are male and female
Iki-Matoran (Acid Matoran)
Colors:lime-green and yellow
All Iki-Matoran are Female
Mag-Matoran(Lava Matoran)
Colors:orange and black
All Mag-Matoran are Female
Here’s a Mag-Matoran I just made