I'm bad at guessing 
Selena:
Looks like from elemental color is having water-based power (may it water, frost, snow, or steam manipulation) 
. If you're a person who connect character's name to their power, then it's moon related (which water is kinda is). Anyway my second guess from her is lightning power.
Zephyr:
I suspect Zephyr has some kind of weather-manipulating power, calling rain, or perhaps controlling wind and breeze. I meant Zephyr means breeze... So... While I suspect there's another alpaca with wind/weather based power, I think this one have different direction of power... Like a restorative one.
Alpha Alpaca:
Alpha... Hm... I'm suddenly thinking Alpha is the leader, the protagonist, or at least the first of his kind. I'm thinking of classic protagonist power. Enhanced strength perhaps, something like Superman? Or maybe super speed? Or maybe he can do telepathy coordination with the rest of his team because he's an Alpha? 
he's the hardest one.
Boreas Starwind:
The name screams "I am Storm's cousin but alpaca, I'm an X-Alpacas!" but who knows? Based on his fluffy design (but more intimidating than the rest), lots of cloud-like design is incorporated; I'm thinking of cumulonimbus. Boreas is the god of north wind and winter in Greek mythology (?), so I guess his power won't be so different; wind, storm, frost, snow, and freezing air.
