Some of my mates suggested I tarnish my logo a little since that would be more steampunky so I wondered about using Vertex Painting in Blender.
This Blender Manual page on Vertex Painting gave me a good overview but I also found out that for vertex painting to be most effective, I had to have a lot of vertices.
It was no good having a really simple mesh like the one I started out with so I had to subdivide my mesh a fair bit.
Vertex Painting is awesome though! It allows you to paint directly onto your 3D mesh – a very natural way to add colour to your 3D models.
Now my logo has a nice bit of tarnishing: