It's probably due to an imported graphic that you're using actually having that specific colour - FM keeps adding it back in because it is being used.
This format of colour naming most often comes in with Indexed colours (usually a PNG or GIF file). It's easier & less frustrating to re-create the graphic and save it as a 24-bit colour image.
Also, to quickly delete these wayward colour defintions, save the file in MIF format, and then use any text editor to delete these from the <ColorCatalog... section - be careful not to remove the first 16 colours - they're special reserved FM ones.
Thanks Arnis! I would never have suspected indexed graphics to be the culprit, but I do have imported PNGs in this document...good to know!
> ... most often comes in with Indexed colours ...
I also see it occur with DXFs and DWGs from AutoCAD.
The colors can persist in the FM file after the infected import is deleted.
Nuking the MIF from orbit usually works.