If you custom mix, you may never match the color again, even if you take careful measurements and keep great notes.
I'm about 5 or 6 locos short of what I want to roster - need a couple S4 and RS11 - so I could do one batch of paint and, with luck, paint everything at once to minimize that issue. Maybe even mix extra to provide for a few future locos if I can store the extra well enough. But you're right, buying off-the-shelf colors would minimize risk. Then again, model paint manufacturers have occasionally been known to change formula. Again, the Model Masters color is closest but I've never worked with it. The red will be easier, I plan on using a pre-existing color - either Rock Island or Milwaukee Road red.
