Though to some may appear reminiscent to “Hoodoo blues” and therefore remind of Doctor John, and in general, music genre associated with African American Conjure community, this article will deal with the power of different kind of blues ( as in blue, the plural form ). The color that comes to my mind, when speaking of Hoodoo, is pale yellow and brownish pastel color, present so much on roots of all kind and old, parchment paper leafs of Hoodoo recipe books. But on a second thought, there is another color so prominent, and respected in Hoodoo. This color is blue.
It can be an “Angelic influence candle” or a haint blue paint in ( and on lol ) folk’s dwellings, or it’s a blue water colored with Laundry bluing ( laundry blue Reckit’s or Mexican anil balls ) or with Bluestone Cu ( SO4 )2. This nice blue color inspires respect, and instills peace among conjurers and root doctors, as well as among arguing clients, and strikes fear into malevolent. Alongside these, well-known uses, I’ve encountered some of these items in "Bend over" or other kind of Influence formulas, and in the Hyatt’s anthropological works, we encounter usage of bluestone in gambling luck. So let’s go through some of the “sources” of Hoodoo blue ( followed by some exemplary formulas, as I do, after all, tend to write practical articles ) And their uses :
Laundry Bluing and Bluestone
Laundry bluing and Mexican anil balls, a washing products, composed of Ultramarine ( or more rarely Persian blue ) dye, and compressed washing soda, entered Hoodoo spiritual works, as a safe substitution for the toxic bluestone, which was used in apotrophaic and gamble luck spells among Conjure community. Although it’s pretty much safe ( as long as You are careful not to come in direct contact with ) to use Bluestone in mojo’s and gamble luck spells, as well as in making Blue water for placing around, for bathes or any other type of product we plan using on humans, or other living beings, we use laundry bluing or Mexican blue balls. You can encounter names such as "Roman vitriol" and "Blue copperas", and they all refer to copper sulphate , a crystalline, sulfide salt of Copper acid, a form of fungicide used in agriculture .
WARNING : If You have any doubts of how to properly handle, bluestone, keep in mind that is corrosive and highly toxic, and that If You decide to ignore this warning , for any possible injury, intoxication or otherwise harmful effect on Your body homeostasis I WILL NOT BE HELD RESPONSIBLE. You can always use LAUNDRY BLUING ( like Reckit’s crown laundry bluing or Mexican balls ) as magickaly equal substitute.
Spirit repelling blue water
Dissolve some Laundry bluing in metallic pans or glass bowls, or metal bowls, and strategically arrange those in places infested with evil spirits to drive them away, while at the same time to beacon the kind ( benevolent ) spirits . A florwash made Copper blue, salt and Blessed water can do wonders as well, and will rid the place of evil, where used.
Gambling charm ( mojo bag )
Hyatt’s “Hoodoo – Conjuration – Witchraft – Rootwork “ entry 13000, teaches us to place ( sew together ) 9 silver dimes with a piece of Bluestone in a red flannel mojo, to have success in games of chance and gambling. 
Aura of Influence
One spell suggests adding :
• Coriander seeds
To a jar or a bottle of Laundry bluing ( meaning either Reckit's stuff dissolved in water, or the liquid laundry bluing ) and leaving it sit for 7 days, then straining. The liquid is used to wash clothes, and when the clothes have dried, one is to wear them to inspire respect, and make others agree with him/her, improve leadership qualities , personal power, and boost self-confidence. 
It can also be used to dye, one of the components of Peace water, meaning either the oil or water. I’ve heard of folks mixing it with Florida water and using that as Peace water instead.
Haint Blue paint
Haint blue is a pale, celestial-marine , to aquamarine paint/color often seen on porch ceilings, doorways and even inside the Houses all over the world, particularly in Southern States (USA), Indonesia, Haiti, some parts of Africa and Mediterranean. There seems to be a neverending discussion between scholars of all sorts, anthropologists, sociologists and occultists about the origins of the custom of painting walls, ceilings or doorways with haint blue, to keep evil dead sprits away.
Does it comes from the Gullah tradition ? Or from the Cherokee beliefs, that every spirit of the deceased ancestors are by nature angry and mischievous. Maybe it comes from old German-Anglo-Saxom customs of warding off similar ( but by no means same ) hag creatures? There are no solid proofs that the belief comes from a single culture-bound system.
In my humble opinion , it might as well be coming from Mediterranean. I live in a Mediterranean country and the common folk belief, if not even a part of culture, here is that angry and mischievous spirits can not cross body of water, let alone sea or ocean water and that they greatly fear pale, aquatic tints and colors. Most likely however seems, that such beliefs are not culture bound at all, furthermore they may be cosmopolite and probably even developed simultaneously In many parts of the world. Because, regardless of the part of the world, haint blue paint has pretty much the s ame purpose everywhere, to repel evil spirits and negate them entrance to a dwelling of a kind, most often house. In States , and some other English speaking areas, these spirits are often called “haints” ( aka angry ancestral spirits ) , hence the name. The paint is supposed to confuse the spirits, and make them think it’s either water or the celestial infinities , what they see in front of themselves, and haints as earthbound creatures, eager to remain on , our physical plane must by all means avoid those. All sorts of demon, and lower-level malicious spirits, likewise fear it.
Indigo powder ( or indigotines )
Indigo tint , although not as light and pale as that obtained from Bluestones, has similar properties in magick and can additionally be used to dye oils and other products. You can get pale-er tint, If You use less indigo powder in base. Indigo powder C16H10N2O2 ( though mostly synthetic for those purposes ) , known as indigotine or carmine indigo is what is used to dye texas ( like Denim for example ) pants/jeans. Source of Indigo are plants of Indigofera genus, or less commonly Woad ( Isiatis tinctoria ) or Dyer’s knotweed ( Polygonum tinctorium ). In magick, it founds popular use in Uncrossing baths, and is often suggested by some Conjurers, for such. It is not, however that much present in traditional Hoodoo, were people will simply go ahead and use Laundry bluing. Also, alcoholature of the indigotines, malkes a brilliant Saturn related ink and a good addition to bath in small doses. It can also be found in some very old, spirit repelling and vanquishing potions and recipes.
NOTES: This article was written and compounded by myself, therefore If You wish to use it elswehre, feel free, but give credits : Shadow of Shadows magick place, or Shadowfirstname.lastname@example.org Credits  from “Hoodoo – Conjuration – Witchraft – Rootwork “ by Harry Middletone Hyatt, entry 13000, paraphrased here Credits  Original spell, in slightly different form can be found in "Encyclopedia of 5000 spells “ by Judika Illes The image is taken by me, and shows Crown reckit blue squares and altar candles in pale blue color, all obtained from occult supplier