How to transform a "finished good" on the fly

One of our products is a solitaire ring.
It is purchased complete and is made of two things: 1) the stone and 2) the mounting.
The stock mounting from the supplier is white and in most cases, we pay for the inventory when it is sold, not on receipt.
Some customers want a yellow ring. For this, we purchase and stock empty yellow mountings.

The physical process is that the stone is removed from the white mounting and placed into the yellow mounting.

How can this be set up systemically? And what is the process to change the color?

Is it that it is 2 Finished Goods or 1FG with 2 versions?

The end result is that we:

  1. purchase the white finished good from the vendor (as FG1 or version 1)
  2. take the white mounting (Raw Material 2) out of FG1 and put it into inventory as a loose mounting
  3. attach the yellow mounting (RM3) with the stone (RM1) as a new finished good (FG2) or a different version
  4. sell the yellow finished good to the customer (as FG2 or version 2)

I would look at using the configuration dimension, and also the process add-on because you could then in have the white mounting going as a by product into stock when you process the manufacture of the yellow finished product.

If it is your product however would you be better off talking to your partner and getting them to talk to you and show you options?