Maybe the train engineer was colorblind and couldn’t tell the difference between “red” and “green.” Happens all the time here in Florida ... ;-)
I'd think colorblindless would be more of a fatal handicap on the high seas or in aviation than on the roads or railways. Incidentally (I've done some research and writing on the subject), one in seven men is colorblind! Far and away the most common is red-green, although there is some rare occurence of a yellow-blue (I think that's what it was) form. Colorblindness of any type is very very rare in women, however.
I asked one of my brothers who is colorblind (to him, brown, green, and red are about the same) how he deals with stoplights. He told me: If the top one is lit, it means stop. If the bottom one is lit, it means go. What has always puzzled me the most is that this brother is also a naturally gifted (and certified) electrician -- he's a whiz at wiring and such, both in cars and in homes. Now how the hell he does that without being able to distinguish the color of the wires is beyond me, but pals and everybody in the family have preferred him for years because his work is always good, and he works for beer, food, or apple pie! No, seriously, when he wires something or troubleshoots a problem nobody else can figure out, he must do it right because his fix-it is always successful. Total mystery to me.