Guys, guys, guys,
To paraphrase Jim Wells ... "Just trust your eyes".
We are making way too much out of the concept of "the perfect color match" -
and even applying it to the color of weathered freight cars.
It's not about the right colors - it's about the right technique of applying a
color in the correct range of choices for that shade. Not only how it is
applied but also when (in the process of weathering an individual car).
Each 'layer' of color produces a different effect - especially based upon
whether that layer is applied before or after some other layer. I'm using
the term "layer" here but I could just as easily have used the term "step
in the weathering process".
And, perhaps most importantly, "Variety is the Spice of Life" (weathering).
In other words - change stuff up in terms of when you do what, what shade
of "weathered grey" you use on this car -vs- the next, etc.
Having said that there is the other side of this coin. Look at any picture
of a freight yard (or a train with more than 20 cars visible) and what you
notice is that there is an overall feeling of same ness ... with a few cars
that stand out - slightly - from the rest. The goal is to have your yards
and trains look like that ... and if the yards do then the individual cars will
"look right" also. We all know that the color of the original paint applied
of any particular RR's "box car red" is often a shade different from any
other road's. But those differences are subtle enough that a quick
glance at a color picture produces the sense of sameness - not the
sense of "PRR's box cars were painted a different shade of Tuscan
than ATSF's". Am I recommending that you use just one color for
BCR for all roads? Absolutely not. Am I recommending that you
use the same mix of color in the same stage of weathering. Absolutely
Repeating myself - it's about getting subtle differences from one car
to the next ... not about developing some "perfect process that you
can use for all the cars you weather" (unless your idea of "perfect" is
to have subtle variations - *G*).