Indigo is a very meditativ colour, which has a strong connection to the subcontious und deep knowledge connected with it. The picture which I often use is deep water where you can not see the ground. You are in a floating tank surounded by infinity, were you loose any sense for individuality. For me indigo is the bridge between heaven and earth. Possible expression associated to indigo are :
Knowledge, mysticism, the third eye.
Several composing techniques and keys work for indigo. The keys are Bm, Dm, Am, Fm and any form of modal and progression in the named keys. Working with ostinato basses and pedal bass with a lot of delay effects are a perfect expression for indigo. Working with beats you might use tempo's between 60 - 95 bpm. On padding sounds go for the deep subfrequencies.
When it comes to improvisation it is recommended to work with visualizations of the color. If you are an experienced player try to play everything with closed eyes and to visualize the selected colour. Your emotional intention and expression has a major impact on the played colour.
Indigo Colour Music on Spotify
Indigo Music Videos on YouTube
Colour Music Meditation
Those who wish can also join the Colour Music Meditation Club. The access is free of charge. There current pieces and videos are published according to the principles of the Colour Music Meditation.