There are different suns in the different planes each with its own colour. But there are also suns of a similar colour above, only more bright, from which these minor suns derive their light and power. The sun indicates Truth directly perceived in whatever plane it may be. It is the symbol of supermind but the Truth may come down into the other planes and then that is no longer supramental but modified to the substance of the other planes -- still it is the direct Light of Truth.
It is hardly possible to say what the supermind is in the language of Mind, even spiritualised Mind, for it is a different consciousness altogether and acts in a different way. Whatever may be said of it is likely to be not understood or misunderstood. It is only by growing into it that we can know what it is and this also cannot be done until after a long process by which mind heightening and illuminating becomes pure Intuition (not the mixed thing that ordinarily goes by that name) and masses itself into overmind; after that overmind can be lifted into and suffused with supermind till it undergoes a transformation.
In the Supermind all is self-known self-luminously, there are no division, oppositions or separated aspects as in Mind whose principle is division of Knowledge into parts and setting each part against each another. Overmind approaches this at its top and is often mistaken for supermind, but it cannot reach it — except by uplifting and transformation.