For those who are looking for lumber that is green in terms of color, treated lumber is the right choice. Pressure treated lumber is sprayed with chemicals that turn the lumber into a dark gray, or greenish, color. Even after the wood has been stained, treated lumber will always retain its greenish tint. For some projects, this may work well; for others, the greenish tint to pressure-treated wood may not be the best idea.

On the Other: Cedar is Greener with Regards to the Environment

For those who are looking for the greener choice in wood in environmental terms, cedar is the best choice. Untreated cedar is just that--cedar trees that have been harvested for wood and turned into lumber. Treated lumber is sprayed with chemicals, some of which have proven to be harmful to the environment. Plain cedar lumber is great for those who want to skip the chemicals and use a high-quality, beautiful type of wood for their project.

Bottom Line

Both cedar and treated lumber are green, just in different ways. While cedar is "greener" when it comes to Mother Nature, treated lumber is actually colored green. Cedar lumber can cost up to three times the price of treated lumber, so for those on a budget, treated lumber is usually the most affordable option in wood.

Source:

The Wood Doctor: Treated Pine vs. Cedar

More Information:

eHow: How to Compare Cedar vs. Pressure Treated Wood