Deane JohnsonIf you want acrylic, Badger Model-Flex has the two UP colors, but I haven't used any so I can't comment on my interuptation of the result. I believe the Model-Flex will dry toward flat which means a gloss clear coat before decaling.
Deano
Several come to mind that are excellent. An old standby that is very good is Scalecoat. It's solvent based, both Scalecoat I and Scalecoat II, just different solvents. Scalecoat I is a laquer, Scalecoat II was formulated for styrene (or plastic) models.
A more recent paint on the market that is well received is Tru-Color, again solvent based, this time Acetone. It handles very nice.
The colors you want are UP Armour Yellow and UP Harbor Mist Grey. Both of the above brands have these colors. Both are excellent in color, my experience with each is that the Scalecoat is a tiny bit darker, perhaps more the color of the top diesels we purchase, while the one engine I painted with the Tru-Color seems just a touch lighter in color.
If you want acrylic, Badger Model-Flex has the two UP colors, but I haven't used any so I can't comment on my interuptation of the result. I believe the Model-Flex will dry toward flat which means a gloss clear coat before decaling. The Scalecoat and Tru-Color are pretty glossy by themselves and probably would be OK for direct decaling if you put them on just right. By that I mean not spraying too dry so the paint is sort of dry before it hits the model and ends up a bit flat or chalky.
Whatever paint you ultimately choose, it's a good idea to get the feel of it on something less important than a prized engine. Learning to get comfortable with the handling of a specific paint is a big part of getting excellent results.
My recommendation is to used the manufacturers own thinner rather than some concoction you put together yourself. If it's worth doing, it's worth doing right the first time.
In all cases, I'm assuming you're planning to airbrush the paint. I can't imagine getting an acceptable job doing this project brushing a paint on.
I need to paint a N scale locomotive with the gray and yellow. What is the closest model/hobby paint available?