Taking the use of filters with the MM to an extreme, this is a tri-colour image, three exposures made by holding three filters, red, green, and blue, in front of the lens and then blended in Photoshop.
I just used a standard red, yellow, and an 80B for the blue, but if I were to consider doing this sort of thing more seriously I would pay more attention to the actual filter values as the MM sensor is already slightly green biased. It produces some very nice colour values, but ideally is limited to still life or very still landscape as any movement at all, from the camera or subject, results in colour fringing.
As for more normal use of filters I do use red and yellow with my MM just to bring out the clouds and losing a stop or two hardly matters given the MM's ISO performance.
Steve