SCS tends to use a range from 0.4-0.6 grey, with 0.5 being the 'neutral' colour. I tend to go darker for things like engine models or visible radiator cores that would be shaded by their surroundings, usually by rendering the AO to the vertex colours (this is a Blender thing). There aren't a lot of cases in which you'd ever go brighter, and fewer still where you'd ever use an actual colour.
It looks like you've pre-lit from a spotlight or something, which makes it always look like light is shining from one direction. You'd only ever do this for a (much) older game engine that doesn't have a dynamic lighting model. Generally what you want to do with vertex colours in an engine like Prism 3D that
has a dynamic lighting model is to do a coarse version of the ambient occlusion so that you can use more of the dynamic range of the texture for actual texture details than for ambient occlusion.
If you want the easiest route to making it 'close enough,' then put the vertex colours all to 0.5 grey and do an AO bake.
As far as material settings go, most shiny/metallic surfaces use diffuse (1.000, 1.000, 1.000), specular (1.000, 1.000, 1.000), env_factor ~(0.800, 0.800, 0.800), shininess 60-80.
Diffuse, you generally don't have to mess with anymore because of vertex colours. You can use this to darken the whole object in a pinch.
Specular is what colour the specular highlight will be if the specular light is white. Usually this will be something grayscale, though you can cheat and tint it slightly (I make the specular colour on my aluminum very slightly blue at the moment). For most shiny surfaces, this will be white or light grey. For things like rubber, I use dark to light grey depending on how shiny I want the rubber to look. My tires and seals at the moment use something in the neighbourhood of a 40% grey I think.
Shininess is inversely related to the size of the specular highlight. High shininess numbers give a very tight specular highlight, low shininess numbers give a very broad specular highlight. SCS seems to use 250 for glossy painted surfaces (truckpaint, etc), 60 for generic surfaces (relying heavily on the alpha channel), and 80 for metallic surfaces like chrome/stainless. I use ~15 for things like dry rubber or where I've set the specular colour very dark (purely diffuse surface). Things start looking kind of weird below ~6-15. Really glossy plastics would be somewhere around 1000+, but you either need a lot of polys or a high-res normal map to get the specular highlight to move smoothly over the surface.