I think this is what the original poster is after, what is the "mid coat" in a candy paint job.
The "colorless basecoat" of today isn't what he is after I don't think, we will wait until he comes back.
I know that matching that pearl and candy three stage (again, only did it a few times) wasn't that big of a deal IF you knew what the actual color was in the original. Doing a let down panel is all you need as the amount of coats applied provide the "Variants" and you pick the proper one. If you had a little more or less pearl or candy in the clear the let down panel lets you sort that out.When you don't know, that is a whole different story. I have sanded off the pearl to the base and cleared it then matched that base color, then matched the pearl with a let down panel.
The true candy paint job you paint the base coat, typically a gold or silver, then spray the "mid coat" candy which is a tinted clear, it's transparent like a tinted window. You apply that over the base in as many coats as you want to provide the color you are after. You then apply a clear clear over that to protect it.
On a pearl, you apply the base coat which there is no typical color, any color you want and everything in the world has been done at one time or another. You then apply a "tinted" clear over that which is a clear with pearl it with the amount of coats you want to achieve the color you are after,then clear clear over that.
A "colorless basecoat" is the way to do this today with modern basecoat clear coat systems, but years ago it was a regular clear. I don't know but HOK may still do it that way, again, I am NO custom painter by any stretch of the imagination but that gets you a little more basic info. House of Kolor- the Official Site for House of Kolor Custom Finishes