Indigo
A lot of people have no idea whatsoever what Indigo looks like, and it often gets missed out of painted rainbows. Indigo is a blend of blue and violet. The true shade is quite dark, and is easiest seen in the clear night sky around a full Moon. There's also a blue flag iris which shows the colour very well. Its higher analogue is lavender... the tone you see in the plant of the same name.
Actually when considering the plant and the effects of indigo and lavender you'll find the Doctrine of signatures at work - the colour and the plant (or its oil) have many shared effects.
Indigo naturally corresponds to the Brow chakra... the 3rd eye... it increases psychism, and encourages philosophical assimilation. It broadens our ability to accept and understand abstract concepts, increases vision, and extends perception.
Physically, it eases migraine, assists with restful sleep (though there may also be an increase in dreaming, induces relaxation and freedom from mundane worries, and works very effectively as a pain-reliever - this due in part to its ability to lift us beyond the purely physical.
It has special importance when we are passing through a spiritually regenerative time, especially if used in conjunction with violet - the violet tones lift us up and away, then indigo allows us to interpret and integrate what we have learned.
