IMO, the inspector should not have failed you for the color of your lampholder socket leads. Does the inspector also want #12 ran all the way to the tombstones as well? If you followed the instructions of the manufacturer's retrofit kit you should pass.
In a recent restaurant troffer LED retrofit I opened a box of four foot LED T8 120V tubes. I took note of the factory sticker that called out the left pin as "N" and the right pin as "L".
I instructed the apprentice to discard the existing shunted tombstones from the troffer socket rail. I told him to wire the new unshunted tombstones with #18 solid black and white harvested from the old instant start ballasts. I told him to go through the restaurant using the sticker as a guide to stab the black for L and white for N.
I followed behind him, lamping and stickering the belly pans. I opened the second box and was horrified to find the factory worker had affixed the L&N stickers upside down, therefore reversing the labelled "polarity."
I checked the instructions and the pins were labelled L1 and L2/N. I was NOT going to redo the apprentice's wiring to match the factory worker's impudence. The 50/50 chance of how the label was oriented on the tube really stuck in my craw.
I understand why the inspector wants the grounded conductor white, but I hope he chooses to be understanding about the color of your socket leads.