Found this list on another site:
VEHICLE CERTIFICATION LABEL:
Exterior paint codes may be listed as a two-part code. The first set of characters listed indicate the vehicle primary body color code. The second set of characters listed (if applicable) indicated a two-tone or accent body color code.
AQ — Arizona Beige (clear coat), F-Series
BY — School Bus Yellow, Mexico sold only, F-Series
CX — Dark Shadow Gray (clear coat), F-Series
F1 — Vermilion Red (clear coat), F-Series
EP — Vermilion Red Solid, Mexico sold only, F-Series
FN — Dark Toreador Red, F-Series
GX — Dark Toreador Red, Mexico sold only, F-Series
L2 — True Blue (clear coat)
LR — Sapphire Blue (clear coat), F-Series
PB — Jewel Green, Mexico sold only, F-Series
PK — Chesapeake Blue, Mexico sold only, F-Series
PY — Highland Green (waterborne), F-Series
UD — Ebony, F-Series
TX — Bright Silver, Mexico sold only, F-Series
YO — Oxford White, Mexico sold only, F-Series
Z1 — Oxford White, Mexico build U.S. sold, F-Series
Z1 — Oxford White (clear coat), F-Series
Z3 — Silver Metallic (clear coat), F-Series
FL — Toreador Red, Excursion
JP — Silver Birch Metallic, Excursion
LD — Medium Wedgewood Blue, Excursion
P5 — Aspen Green, Excursion
ST — Estate Green, Excursion
TK — Mineral Gray, Excursion
UA — Ebony, Excursion
YZ — Oxford White, Excursion
Later,
BK