I have an original, 1911-1912 STOVER saw-rig cart, that has remnants of red paint on the wood. However, there's no paint to be seen on the iron wheels, so that color, I couldn't tell you. Personally, I'd put several clear coats of Spar-Varnish or something like that on the wood to bring out the wood grain & paint the wheels red, to match the engine, but that's me.
Mate im not married (nor have been) but I think this might be a good time to let your wife choose the colour! maybe even classify it as "her" engine. Hey it works well with girl friends it should work with wifes??? Shouldnt it?