What is the best color combination on my computer to help reduce eye strain?

Warmer. Many people feel the warmer (lower k temperature) colors are more pleasing. There is a setting for this under your monitor control. Also, some feel a slight yellow tint to computer glasses reduces glare and increases contrast. Making sure the resolution is set to a native value on lcd displays makes text sharper as well.
Colors. In general, it is a matter of preference. However, some artists would say that blues and purples are more soothing to the eyes, whereas red and oranges are less soothing.