Lightfastness rating according to the American Society for Testing and Materials D5098:
I=Excellent II=Very Good III=Does not conform to ASTM D5098.
Ratings are based on the color at full strength. Some colors will be less lightfast when used as a tint (mixed with white or other colors) or if used as a glaze (mixed with clear mediums).
* * Cadmium colors may fade in the presence of moisture or acid rain and are not recommended for exterior use.
+ Indicates color is top rated for exterior use.
Within the ASTM Lightfastness rating of I=Excellent there is a wide range.