Followup: Went over to Einmalig Porsche today and looked at various retractors. When I pulled the webbing all the way out, I could see the end of the webbing is held in place just like the 914 retractors. This means I can make the color change by changing out the webbing and have the hardware resewed at an approved place.
Each side had 10' of webbing. Seat Belt Pros
(
http://www.gotbelts.com/colorchart.html)
sell it by the yard in a variety of colors.
Did this with my 914, and it worked well.