Indigo is a great colour to see. Aura wise, it relates closest to the dark/deep purple I see that represents angelic protection. I interpret it to mean that the guides and angels around you are keeping you safe and keeping you attuned for their messages.
When focused on the chakras, indigo shows up in the third eye. Located between the eyes, this chakra relates to our ability to focus on the big picture. It deals with our intuition, imagination, wisdom and ability to think & make decisions.
The third eye chakra can be cleansed by eye exercises, purple coloured fruits (grapes), lavender flavoured spices or tea and (my personal favourite) chocolate. Essential oils that help heal the third-eye chakra are star anise, lavender, eucalyptus and rosemary.
Gem stones that work best to heal and stabilise the third eye chakra are Azurite (which helps awaken psychic abilities and provide insight. It helps the flow between chakras and helps connect us with our spirit guides) and Lapis Lazuli (which assists in past life recall and releasing karmic debts).