Zor, Ken, yes the light plays tricks on you and all my determinations on if I had the correct color where done in the natural day light. The difference in color is very apparent to the naked eye. Most of the observations of different color from one moment to another where, as I have stated, caused by light, and the yellow mind game
In a life long ago I was married to a pro photographer and I know what light can do to a pic and other objects.
As to the mixing, this paint is an equal part of two, part "A" and part "B" I cant explain being I mix them all the same, currently the smaller batches (1-2oz of part A and 1-2oz of part B with 1-2os of reducer) have been the yellow and the larger batches of 4-5oz have been the butterscotch. But the very first batches that I painted the fuselage where both 5oz batches, and the result was the yellow. I did keep a memento of the butterscotch (just so folks don't think I am crazy). The insides of the cowl engine doors are the butterscotch, and one can tell right away.
I have been mixing with portions of paint from small cups (1oz cups) and when I do the wing I will use a pint mixing cup that has the 1-1-1 formula on it so that I get as close to exact measurements, but again the first batch was not done this way and it came out right.
So I am chalking it down as Yellow is one hard paint to work with. Yes Zor I will test the paint before I spray the wing, if it doesn't present as the yellow I will not use it, you can tell right away. I will mix up another until I get yellow or run out of paint.
TB