I have been down this road with SP engine colors and can say that the red (I think actually designated SP "Scarlet") is an easier match than the orange - not least because Lionel used its own idiosyncratic color mix. Also you have to bear in mind that the finish is not matte or gloss but more like semi-gloss.
For the red I'd use Tru-Color's TCP106 Daylight Red; they also make a TCP107 Daylight Orange. These are meant to be airbrushed but if shaken thoroughly and applied quickly to a small area can be brushed on. Clean up with acetone as these are solvent-based paints sometimes described as "lacquer" but the formula is Tru-Color's own proprietary mix. Another airbrush paint (acrylic) that I have used for very small nicks is Badger Model Flex 16-36 SP Daylight Red. With the orange I found that it was necessary to look around for a shade that, whichever railroad it was attributed to, actually was a close match for a specific Lionel engine.
I am not sure if you'll be able to find anywhere the old Floquil or PollyScale SP Daylight colors that were designed for brush application but they were fairly user-friendly.
