Why green, Now that is interesting for there is many reasons the changeling horde has adopted this corrupted toxic green as its primary color....
*the changeling pulls out a list of reasons and hands it to wintersmoot*
1. It was originally the color of the magic that performed the ritual, It originally was a emerald green but when we were marked with this corruption it changed to a toxic corrupted green, most changelings have there magical abilities manifest in that shade...But some have managed other colors such as purples and blues.
2. Green looks good in the hives general pallet color for it compliments the lovecraftian architecture, the long tunnels that maze throughout the hive, and the glowing vats of DNA that we use to mix and change changeling breeds.
3. It is erie, otherwise it says something is not right like it is a ill omen or a lurching doom, Or it may suggest the horror of losing yourself to a corruption that snakes within your being
4. Green is the best for mind control, No joke green especially a toxic green has a higher degree of catching the eye drawing them unknowingly to the sight of it, But it is only effective after direct eye contact with a changeling.
5. It fits with the way we look truly as obviously we can change our form, But in all honesty are real forms are corrupted shells of what we used to be as i told you in the story, we had changed a lot more since then taking more reptilian if not insect like traits.
6. This should help explain a bit..
http://tvtropes.org/pmwiki/pmwiki.php/Main/SicklyGreenGlowThat should cover it, any other questions. the changeling takes a drink before looking for something good to eat.