My dad gave me a whole box of coloured contact lenses, in various colours, because they were getting near to their expiry date (he's an optician). The emerald green ones were pretty cool, but my eyes are so dark brown that most of them looked crappy.
I have prescription green contacts ( freshlook brand ) and I have red and other colors for halloween and stuff xD I love them but they can be a little uncomfortable.
Ahaha, my mom's cat rancher friend has brown eyes and uses ELECTRIC BLUE contacts. And her eyes are always blood shot. Blue is her fav. colour. XD
I've wanted to try wearing patterned contacts for Halloween, like the kind with swirls and cat-eye designs and stuff on 'em. I've never used even regular contact lenses before, though; I just wear glasses. I might want to try coloured contacts to make my eyes a brighter green, though. My eyes are kind of a mossy green. pokes profile pic
I have brownish eyes and I've used grey and green contacts before, I actually have a picture of me wearing the green oneshere. (Yes, it is rather blurry&that is a green streak in my hair XD)
I have grey eyes, and I used to have turquoise and hazel contacts. They worked well, but I have light colored eyes so they may treat you differently. The turquoise was pretty, but I HATED the hazel. It made my vision foggy and looked like poop :(

I have brown eyes and I used to have blue contacts before. I think they were Acuvue? Not sure. They also had a prescription on them so they helped me see better.
People said they looked real, and they were pretty nice looking. Some days I couldn't feel them, other days I could and some days it was almost unbearable. I also use regular contacts, and I have to say the colored contacts were uncomfortable compared to them. I could always see the color on the edge of my vision. Also if I wore it for too long they would start sliding around. >.< I even had to take them out one day towards the end of school because the were bothering me so much.
Edit: LOL So I was looking at the picture again and it looks like a really horrible photoshop, but those really were my contacts. xD