Some filters like Melitta come in a white version and brown kraft color version. At a time when white paper might have been bleached with chlorine, this was important. But these days white color filters are blanched using an "oxygen whitening" process with specialized equipment that does not use chlorine or harsh chemicals. Natural color papers tend to impart more paper taste to the coffee too, but all types of filters benefit from being rinsed with hot water before brewing.