What is the correct color for 67-68 lower door vents

To paint the plastic and have it last, you will need the SEM dye products — surface prep, primer and spray dye. I painted the dash top vents navy blue on my convertible and they came out great. You can just pick a dark red to match your doors (assuming you have the factory red paint on the doors and not some random bright red paint) — even from the factory the plastic parts didn't exactly match the painted metal parts.