Different colors can trigger different responses. Our veiled cham, Guido, tolerates handling pretty well. I learned (or, rather, he taught me) that he responds better (or worse) depending on what colors I am wearing. He changes color according to his mood and frame of mind, and he assumes I do the same. He looks me over each time and seems to try to assess my mood and intentions. Friend or foe? Therefore, if I approach him wearing a color he finds offensive, it puts him on the defense, and can even scare him. So I keep a few loose fitting shirts handy in neutral green tones. I can slip them over whatever I'm wearing, before I approach him. This seems to make a big difference.