Here's Lido Gold (17656) from the Chassis Internal Service Bulletin Oct. 1970:
Attachment 274160
68XX does not mean 'custom/special/paint-to-sample/non-standard paint'. It's simply the most recently used Porsche color number (in this case 6822 used for Champagne Yellow in 1968 and 1969) for that particular shade. Only when we know what Porsche charged for a color brought back from the dead will we know whether they considered the reuse of an older color code optional or paint to sample. Did they charge for an optional color or did they charge more for a paint to sample color? As usual the answer lies with the financial dept.