"Muddy" color can be both situational or/and genetic. It not only refers to the color itself---but other qualities of color as well. Back in the 80's it referred to brown/bronze tones in yellow flowers. In the 90's it was more the dullness of color in the red flowers. Since then, it has broadened to mean colors that are not distinctly that color--and are unpleasing to the eye. Pinks that are not clear and true, reds that are not bright, clear, and saturated, yellows that are intense, clear and bright, etc. etc.. Color pigments are in the cells on the surface of the flower. By breeding background color of white, the colors have become much more clear and true. Pat Stamile was a pioneer of that effort. Many of the really great colors that we find today are on a white background. Solid color flowers are becoming more and more saturated. As the pigments get more saturated--covering the white background--the more intense the color becomes. The reds we have now are wonderful! The big challenge now is to get patterned flowers that have clear, well-defined, colors that are each bright, and saturated. We have yet to see a clear pattern on a pure white background. the colors of the pattern tend to either taint, or bleed into the background color. Red eye/edges are closer to the goal. Some of the Salter's cultivars are great!
