[fletch]

Two things will affect the colour your camera captures. The exposure and the white balance setting.

Exposure is very tricky at sunset becuase the light is rapidly changing and the sky is often a lot brighter than it appears leading to washed out skys and dark feature less shadows. If the sky is over exposed this can cause it to lose saturation and look dull and colourless. Due to the complexity of sunset light there are no magic bullet settings or camera modes. Auto Exposure Bracketing (AEB) will help though as you can capture 3 different exposures at once to ensure you get the shot.

White Balance will affect the colour of an image, too cool an it will look blue, to warm and it will go orange. Try the daylight setting and if that doesn't work you will need to set a custom white balance.

Shooting RAW can help in these tricky situations as you have more oppertunity to adjust later and you don't need to worry about your WB setting in the field.