Painted D&RGW Caboose Grab trons and Handrails

My son had a question on what the "rules" were for painting handrails and grab irons a contrasting color from the normal color the body was painted on NG cabooses . . If I look through Volume V, I see photos up until the mid 30's where almost all have those items painted the same color as the body. However there are 1938 photos with them painted a lighter color, and a photo from 1939, where they aren't. So there must have been a transition period. Was this a mandated requirement, or something the Rio Grande did on their own?

So if the goal is to make these safety items easier to see in low light, why is the brake staff also painted? Seems like you wouldn't want to grab onto that. I was looking at a photo of one caboose with a caboose-red brake staff and the wheel white, and it looked weird. Was there a rule about that? Then there are the cut levers, sometimes the ends are painted white. Sometimes not.. Why not just paint the whole thing?

While we're at it, on DRGW cars when was silver vs white used? I keep forgetting. Volume V isn't much good for that.

Bill Kepner