how do I colour using vertex paint? I've been looking around for a while now and its so hard to navigate. Anyway, how do I colour in models? I've tried the vertex paint thing but it disappears after I have selected another part.
Using Blender Render, To see vertex colors in 3d viewport you need to be at least in textured viewport mode...although you can paint in solid mode also. 

And to see  vertex colors in render, your material needs to have "vertex color paint" option enabled.