I covered my 80 series with the U-Pol tintable and found that the color was no where near the darkness of the stock 97 Emerald green of my truck when applied. I used urethane paint as the tint. The tintable version of U-Pol is greyish in color and it makes sense that it will lighten any color/tint added to it. Also, I couldn't have added any additional tint unless I dumped some of the liner out of the bottle and still had room for the hardner and shutz gun.
I'm about to cover a white truck and I hope this isn't as much of a concern in white. If anything the greyish color of the liner would slightly change the brightness of the white.
GLTHFJ60,
How much white paint/tint did you end up adding to each bottle of liner? Did you have to dump out any of the liner to make room for the tint?
Try using just tint (paint without the binder in it) instead of paint. It should improve the color match.