Chromatic orb mechanics

Is there a thread somewhere discussing the RNG mechanics of chromatic orbs/ using them to get socket colors not of the armor type (ie red sockets on int armor)? I have heard it is more difficult to do so but just how difficult is it, or is it even possible? I just spent 85 chromatic orbs trying to get 2 reds, a green, and a blue on an int circlet, and it just didn't happen. And that's not even trying to get NO blue sockets, just primarily red sockets. I can't even imagine having to get 4 reds on that.

I did a thread search and lol'd at the guy that was upset he couldn't get the colors he wanted in 4 tries...