What I like about train watching is that everything is unique. Every freight car has its own history on its side. There are white spills of minerals or grains coming down. Oil is dripping from the hatches on the tank cars. Some cars are covered with rust completely while other have rust near the top. There is old black rust, mostly brown rust and new orange rust. Flat cars carry loads on top. There are trucks and sometimes military vehicles, and yellow machinery for maintaining the tracks and ballast below them. There are hopper cars full of coal (often long trains of just black hopper cars going to power plants in the east.) Gondola cars from steel mills have damage where heavy steel loads have shifted, putting bulges coming out from inside. All of the these things are unique. Nothing is the same. If you like old barns, it is like a parade of them.
The Union Pacific locomotives are painted like school buses in yellow and they are cared for because they are far more expensive that freight cars. They have their history with fading paint on top and black stuff coming down from their diesel exhausts. Big red numbers indicate the locomotive types.
Graffiti is everywhere because cars can stay in place where they can be painted with spray cans. Some graffiti is so artistic that it looks like some art school person must have painted it. Most is done in vivid colors and it is done in simple letters outlined for drama. The white squiggles for gang graffiti look good when they are examined closely. I'm not a fan of graffiti because pride and workers are expensive and it is rarely painted over unless it is obscene. If you compare our railroads to those in Europe there is less graffiti there.