Veileds have resting colors and may change their pattern and color to different stresses in their lives. If there is something they are unfamiliar with it or you take them out of their "territory" may make them change colors and patterns to some extent. For instance, if you take one outside, it will likely react by changing its color and pattern somewhat. They are being on guard for whatever could happen to them.
One male running into another male will result in the colors becoming bright and the body flattening. The tail may coil in and out, one hand will often be held close to the chin, the gular pouch (under the chin) will inflate, the chameleon will likely hiss and gape. If the other male doesn't give way then there will likely be a confrontation.
If a male meets a female he will brighten his colors, flatten his body and approach her head bobbing. If she reacts appropriately he will mate with her.
A female that is receptive to the male will keep her body thin, likely hug the branch, raise her bum up slightly and slowly walk away from the male while keeping her green background color.
If the female is gravid/non-receptive, she will turn almost jet black in the background, hiss, gape, sway back and forth...and if the male doesn't pay attention to these warnings, she will lunge at him.
Hope this helps!
