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I've always lived in New England but I've never heard of painting a shingle as a method of repelling woodpeckers. I did find these links on preventing/repelling woodpeckers:

http://www.ehow.com/how_4464360_repel-woodpeckers.html

http://www.ehow.com/how_1031_prevent-woodpeckers-pecking.html

And also saw this:

Treatment of the siding with pentachlorophenol or other wood preservatives seems to repel woodpeckers as well as providing insecticidal and wood-care benefits.

Sticky, paste-type repellents applied in the damaged area and for several feet on either side have been effective but may melt and run in hot weather causing stains to building materials. The birds are not trapped by these substances but dislike the tacky footing.

Commercial products, available at home and garden shops, have objectionable tastes and odors and may discourage woodpeckers.

Good luck!