A bit of a de-rail:
My grandmother would use a bit of bluing in the final rinse after shampooing her beautiful white hair, just enough to tint the water a very pale blue. the origin of the phrase, "blue haired ladies"
And always in the rinse water of the "lily white" batch of laundry, a little darker blue. That stuff is potent, even more so than food coloring.
And just for fun,
"In a glass or plastic bowl, put some pieces of coal, coke (charcoal-like substance, charcoal, porous brick, tile, cement or sponge.
Day 1: Over the base material, pour two tablespoons of water, two of table salt (iodized or plain) and two of Mrs. Stewart's Bluing.
Day 2: Add two more tablespoons of salt.
Day 3: Pour into the bottom of the bowl (not directly on the base material) two tablespoons each of salt, water, and Mrs. Stewart's Bluing, and then add a few drops of mercurochrome, vegetable coloring or ink to each piece.
By this time a beautiful flower-like growth should have appeared. If all the conditions are not ideal, it may be necessary to add two tablespoons of household ammonia to aid the growth. A free circulation of air is necessary, and these formations will develop better where the air is dry.
To keep it growing: Add more MSB, salt and water from time to time. It will "bloom" indefinitely into beautiful rosebuds, coral and crystal. Try it!" From Mrs. Stewarts Bluing website. for some dumb reason (the faulty finger/keyboard interface), I couldn't do a direct link.
That bottle of blueing was a staple at our house,and I have made many a crystal garden. Wonder if I still have a bottle in the deep recesses? I should start another.
and I have cooked many a kettle of Faultless starch for my dad's and brothers' dress shirts before the days of perma press.