Using a PL Filter
One more factor that really enhances the brilliant autumn colors is the fresh and beautiful clear skies. Nothing says autumn better than a landscape composition that includes the clear blue skies and the reds and yellows of leaves. However, if you compensate the exposure to emphasize the foliage colors, the color of the sky in the picture can seem brighter and more faded than what you actually saw. This problem can also be solved by using a PL filter.

Enhance the color of blue skies using a PL filter
Using a PL filter you can emphasize the color of blue skies. While checking the monitor, turn the filter frame until the color of the blue sky seems deep enough and then take the picture.
The PL filter eliminates unwanted reflected and polarized light making the sky seem even more blue. When taking pictures of autumn scenes, a PL filter emphasizes the blue in the sky while at the same time avoiding the reflected light from the leaves surfaces. The result is a picture where both the blue skies and the fall foliage come out in vivid, deep colors.

Useful things to remember

The filter is most effective on light coming at a 90 degree angle in relation to the main line of sight of the camera. In most cases you will achieve a high effect with front-lit skies. However the effect will be almost negligible with backlit skies. Open "Useful Tips: Using filters"
When using a PL filter, turn the adjusting frame while checking the effect on the monitor or the viewfinder and only then take the picture. The effect cannot be checked on optical viewfinders.
When you use a PL filter, the amount of light will be less than under regular conditions. As a result, the camera sets slower shutter speeds and this can easily lead to camera blur. Try using a tripod or take other measures to avoid this.
There are several types of PL filters but with a digital camera use circular-type PL filters.