(Click on photo to see a larger image of the lovely Radha London Isvara)
santah sadaiva hrdayesu vilokayanti
yam syamasundaram acintya-guna-svarupam
govindam adi-purusam tam aham bhajami
I worship Govinda, the primeval Lord, who is Syamasundara, Krishna Himself with inconceivable innumerable attributes, whom the pure devotees see in their heart of hearts with the eye of devotion tinged with the salve of love.
The Shyamasundara form of Krishna is His inconceivable simultaneous personal and impersonal self-contradictory form. True devotees see that form in their purified hearts under the influence of devotional trance. The form Shyama is not the blue color visible in the mundane world but is the transcendental variegated color affording eternal bliss, and is not visible to the mortal eye. On a consideration of the trance of Vyasadeva as in the sloka, bhakti-yogena manasi etc., it will be clear that the form of Sri Krishna is the full Personality of Godhead and can only be visible in the heart of a true devotee, which is the only true seat in the state of trance under the influence of devotion. When Krishna manifested Himself in Vraja, both the devotees and nondevotees saw Him with this very eye; but only the devotees cherished Him, eternally present in Vraja, as the priceless jewel of their heart. Nowadays also the devotees see Him in Vraja in their hearts, saturated with devotion although they do not see Him with their eyes. The eye of devotion is nothing but the eye of the pure unalloyed spiritual self of the jiva. The form of Krishna is visible to that eye in proportion to its purification by the practice of devotion. When the devotion of the neophyte reaches the stage of bhava-bhakti the pure eye of that devotee is tinged with the salve of love by the grace of Krishna, which enables him to see Krishna face to face. The phrase "in their hearts" means Krishna is visible in proportion as their hearts are purified by the practice of devotion. The sum and substance of this sloka is that the form of Krishna, who is Shyamasundara, Natavara (Best Dancer), Muralidhara (Holder of the Flute) and Tribhanga (Triple-bending), is not a mental concoction but is transcendental, and is visible with the eye of the soul of the devotee under trance.
(Sri Brahma-samhita 5.38 and Purport)