You have to really have a passion for color match, either that or a serious God given talent.
You mention the sun over artificial light, the guys are work KILL ME they use that F-ng light all the time! The sun is right out side, and there they are using that F-ing hand held light. GRRRRRRR no wonders they can't match worth a crap. And Ray, another thing is using the clear you are going to use on the frigging car! The film thickness, the yellow (I know it shouldn't be there but it sometimes is) of the clear, it is very important to dupicate exactly what you are going to do on the car it's self. What sense does it make to spray the color different than how it will be sprayed on the car?
And of course practicing spraying it out with the same air pressure and distance. Again, I have seen guys bombing it on the spray out card coat after coat seconds apart just inches away so it covers fast. Are they going to paint the car that way? How do they expect it to match?
I have a guy I work with who has beached about the paint not matching when he has sprayed a spray out card that DID match. What do you say to a guy like this? I calmly asked, "How could the spray out card match and the paint on the car doesn't"? SOMETHING changed between the spray out card and the car, SOMETHING changed. He honestly believed it was the paint that somehow changed, I am not making this up!
Oh now you have me started, I need to go relax.