Chakras are rays.... sort of

[Plenum]

You have outer prana, and inner prana. Where they meet determines your experience of reality. The inner prana descends downwards through the chakra system and equals your will, or inner seeking.

anagogy; how do you understand prana?

* is it the same 'phenomena' as is described by other words such as chi, qi, etc etc in other traditions

* is it a form of spiralling light or intelligent energy

* is it the 'background radiation', full of the unexpressed potential of the Creator, waiting to be 'actualised' by the entity through which it passes through

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to speak to the original point of the OP, the rays have a different meaning in higher densities (functional). But the energy centres (what we call chakras) are still seven in number and the same color. So 4th 5th and 6th density entities have the same 7 energy centres we do, but as anagogy says, they would filter out a different 'beingness' or 'experience' or 'understanding' via the prana.

Rays, as you surmised, are simply spectrums of energy or consciousness associated with a particular vibratory level (density). So your sixth chakra or energy center is a filter for indigo ray energy expression.