Set your camera for auto ISO, Spot meter, Tv, and aim for the grayish part of the body for a shot like this. Or use TAv so you have control over both aperture and shutter speed. Once you've set your focus, hit the AE-L button and recompose your shot. It isn't always a perfect solution but works most of the time for me.
The second two shots look over exposed and the shutter speed in the first one is way too slow. Letting the ISO roam will help correct this. As for any Purple (which I don't see much of), there are situations where any lens will do it. It can be corrected in post processing fairly easily.