Thank you, David Campbell! I notice that when I wash a bowl stained with
blueberries (Vaccinium spp.), the water is colored blue, then green, then a
light yellow as the dye is diluted. Possibly a similar phenomenon to that
of shell dyes, though less permanent.

The Portuguese man-o'-war (Physalia spp., a siphonophore) yields a similar
range of colors when stranded on the beach. Caution is certainly advised in
handling them, as the stingers can be painful and dangerous.

The purple seasnail (Janthina spp.) yields apparently the same colors on
the beach. Is this all one dye?

Andrew K. Rindsberg
Geological Survey of Alabama