IIRC, sometime in the early 60's this became required. I will have to look through my AAR stuff to get the exact day. Many railroads were already using it before the requirement was published.
Modeling BNSF and Milwaukee Road in SW Wisconsin
I just happened to have the NKPH&TS "Cabooses" book by Willard A. Harvey in front of me. Several photos show wood cabooses in 1941 with "contrasting" color* handrails, even on the "War Emergency" cars built from box cars.
*could be white?
If I find more precise information I'll update this. I have books on B&O and PRR cabooses. Sometimes you get lucky and find an "obsolete-revision" change made on a drawing and that will give you a close reference to the time the change was made.
B&O's first "wagontop" caboose was built in 1935 and the handrails and grab irons were painted the body color. In 1936 they built a second one, body color gray and handrails black. The caption states that it would be another ten years before B&O adopted safety yellow for all caboose handrails (1946).
All of the photos of cabooses in the Color Guide to New York Central Freight Equipment show yellow grab irons and hand holds. The earliest color photo is 1953.
Good Luck, Ed
When I get a chance I'll see if the AAR standards for safety appliances book I have makes any mention of paint color.
[edit] The 1940 Car Builder's Cyclopedia has a chapter covering application of safety appliances on caboose cars and there is no mention of a required contrasting paint on handholds and ladders.
A google produced this tread regarding locos.
Sorry I never recall how to make clickable...and I'm trying xyz... which won't seem to work(?). EDIT: Got it! It has to have the "url" stuff when posted; i.e., adding the url stuff as an edit did not work.
http://cs.trains.com/mrr/f/13/t/216958.aspx
Paul
Modeling HO with a transition era UP bent
When did this sort of paint come into being?
Henry
COB Potomac & Northern
Shenandoah Valley