I do not believe your color variation was caused by sanding. I think it was caused by touch up gel coat being applied that is not the same color. Theoretically colored gel coat is solid in color and when applied is being put on as a coating that should be the same color all the way through its thickness. It looks like you may have had a scratch there and the dealer opted to scuff the area, apply gel coat over the top of the scratch and then sand and buff out rather than trying to sand a scratch that may have been too deep risking sanding through your original gelcoat.
It is amazing the different hues of blue there was and the way that color changes in different lighting conditions. Love the color but wouldn't want to care for it.
There was a flaw in that spot. It was never touched up. By flaw I mean there was a spot the size of nail head that looked like it may have had a bubble or some dirt in it. I am positive they didn't try to touch it up, They only wet sanded it because I was there when they did it. That's also why I mentioned I thought they were more aggressive than they needed to be..........meaning I think they could have sanded it less and with a finer grade of paper. But, it looked fine when they were done with it. The discoloration only showed up with the halogen light.
There is just something about this color that makes it totally different than any other gel coat and I believe it's the translucency. In the past Robf300 on our board, who does fiberglass work for a living, has mentioned how strange this gel coat looks right out of the can.
But since there is nothing I can do about any of this, I want to make sure that others with Blue/Purple hulls are aware of some of these strange characteristics. I think the color is beautiful personally, but it needs to be cared for a little bit differently than most other gelcoats and that was the purpose of my original posting.
Dave