The only place I can find a "fluffy yellow" signal aspect in the rules is under 1.5, so the question becomes was it imperfectly displayed or observed?

As cheap as Scotchlite is, I've always wondered why all the railroads don't put red "A" plates on absolutes and a yellow number plate on the others, directly under the top signal head. This would make it obvious if there was a dark or malfunctioning signal at night. Soo Line put a small green rectangular target on their switch stands, which made it much easier to find switches in the dark or inclement weather and know how they were lined.

I notice UP seems to be putting a single red signal at the end of a multiple main track merging into another main so the best signal you can get is red over green - "approach converging" suggested by a much earlier discussion. Strangely all the intermediate height signals to leave sidings around here were replaced by UP with the standard tall signal masts. It used to take me at least 6 months to really learn 100 or so miles of track that I might run a few times a month. I can't even imagine learning a thousand miles including every speed restriction and signal location, much less where the train will run on you. I wonder how many truckers can do the same?

Common sense seems to be in short supply these days.