Thanks for your reply Forseti. Most informative, as always.
Now Olympus cameras do have tonal settings, but these are labelled as Vivid, Natural, Portait, Muted, Monochrome and Custom. I can also adjust the contrast, sharpness and brightness too. The only adjustment I made there was to the sharpness as with one of my other lenses it has a can sometimes look a little soft. I also tend to try and switch the noise reduction filter to either low or off as I find this can also soften the image.
Now for the shots in question I changed between the vivid, natural and portait settings on the tonal choices but the result was almost the same as under-exposing was concerned.