This filter was originally designed to improve the picture of a HDV camera that produced a rather noisy chroma signal. Fortunately chroma noise is easy to fix without much loss of picture resolution. Start by increasing the Chroma Blur until the noise disappears. Then try backing off the Spatial Chroma Amount until just before the noise reappears.
Spatial Chroma Amount
0 to 100
This controls how much of the Chroma Noise Reduction is mixed with the original image.