Wool is a durable, NO VOC, easy-to-wash carpet option. Most commonly they sort the sheep and sell all natural colors, hence, no powder blue:
Even though synthetic dyes are safe, non-toxic, and have virtually no negative impact on the environment, there are people who want to be as environmentally benign as possible. Natural dyes are not used because they tend to rub off on other fabrics and have poor light-fastness properties that require heavy metal mordants (to help natural dyes affix to the fiber) so they aren’t necessarily an environmental improvement.
Here are some styles and color options from Unique Carpets: