Just to expand a little on liber and Orb's posts, from
this doc:
The four entries for each material are as follows:
• The first line specifies the diffuse material colour. This is the colour that is diffusely (in all directions) reflected from an illuminated surface.
• The second line specifies the ambient material colour. This is the colour of an unlit surface.
• The third line specifies the specular colour. This is the colour of light reflected by a polished surface into a narrow beam. The power entry specifies the width of the cone into which specular light is reflected. Higher values mean a narrower cone, i.e. sharper reflections. Typical values are around 10. If omitted, the default value for power is 0.
• The fourth line specifies the emissive colour. This is the colour of light emitted by a glowing surface.
You will have to fiddle about with the numbers to get the effects you want, remember to test them in day and night.