You may be able to get new covers which are white from Airstream, Inland RV, Out of Doors Mart or other vendors of AS vintage items. Also using "daylight" LED bulbs with yellowed covers gives a nice warm light.
This is my first post! We've been AS owners for 2 weeks now. You can find new covers by Progressive Dynamics RV and Marine Power Converters and Chargers The white covers come 2 to a pack (part #PD 305) are about $2.50-$4 a pair from Camping World, Amazon, etc.