Arnold Menke has provided a list of when the GS locomotives were painted black or lost their skirting.

SOUTHERN PACIFIC MODEL PAINT COLOR INFORMATION
DAYLIGHT PAINT SCHEME
Common Color Name	SP Name	Drift No.	Duco or Duluxe No.	Pantone No.	parts	Formula	Notes	Reference
Daylight Red	Daylight Exterior Red	28	88-5451	193	-	FL R-135 SP Daylight Red	Socony Red, Golden State (over aluminum color)	Bill Kelly, Ken Harrison, Tony Thompson, Bill Havrilla
-or-	-	-	-	-	-	AP 428 Socony Red	-	Ogden Lamont
-or-	-	-	-	-	1 part	FL R-30 Reefer Orange	-	Bill Havrilla
-	-	-	-	-	1 part	FL R-20 Caboose Red	-	-
Daylight Orange	Daylight Exterior Orange	29	-	137	-	FL R-134 SP Daylight Orange	Daylighter; MOW Orange, post 60's	Tony Thompson, Ken Harrison, Bill Kelly
-or-	-	-	-	-	-	SC-30 SP Daylight Orange	-	Bill Havrilla
-or-	-	-	-	-	-	PS 414185 Daylight Orange	-	Ogden Lamont
-or-	-	-	-	-	-	AP Daylight Orange	-	-
Lettering Gray	Exterior Silver Grey	151	-	-	-	-	All Letters, Numbers and Striping	Bill Kelly
Black	Daylight Exterior Black	6	-	-	-	FL R-10 Engine Black	Roof, Underbody	Bill Kelly
Green	Dark Jade Green	27	-	-	-	-	Cab Interior	Bill Kelly
White	White	-	-	-	-	-	Service connection lettering on side sill	Bill Kelly

-- To da trains! --