Lloyd~ Obviously emerald green. It made it's way from a head canon to actually play part in the show. Although if they didn't make that canon it should have been purple... *He would look better with purple eyes in my opinion, but I'm fine with green*
Kai~ Green. Just green. I've always seen his eyes as green with a slight tint of brown where his scar hit his eye.
Cole~ Hazel. Since he is the Master of Earth why not? He has mixtures of green and brown fitting perfectly together. His father said it was the one thing he took from his mother...
Jay~ Electric blue. I see some saying brown or bi eye, but I prefer them to be blue since literally it's his whole persona and I would never want him to change it =)
Zane~ Neon blue. Simple. He's a nindroid nothing else to be said.
Nya~ Ocean blue. We she was born she had brown eyes, but after a while they turned blue for no good reason. It still is a mystery to this day...
( I realize that none of them have brown eyes.... Welp if it helps Dareth has brown eyes )