For FDE or ODG, you can try dyeing a white fin with RIT dye recipes found on the internet. Sorry that I don't have a better solution...
NOTE 1: Photographs show the right-handed version.
NOTE 2: This accessory is made to conform to the CA DOJ criteria to prevent a pistol style grip, but has not been approved. To be part of a "featureless" configured rifle, this accessory should not be used with other features defined in Penal Code section 12276.1. Please consult your local laws and regulations to ensure compliance.