Dark blue occupies a charged and polyvalent position in the depth-psychological corpus, functioning simultaneously as a chromatic fact, an alchemical stage-marker, and a metaphysical designation. Hillman’s extended meditations in Alchemical Psychology constitute the most systematic treatment: dark blue is located transitionally between the nigredo and the albedo, carrying the residue of mortificatio into the whitening process while manifesting the soul’s own complex interiority. It is the color of bruises, of jazz, of melancholy sobriety—yet equally the color of the imaginal firmament, the unio mentalis, and Dionysian depth. The Emerald Tablet’s formula that black exceeding white by one degree produces a sky-blue establishes dark blue’s constitutive relationship to putrefaction and aspiration at once. Homeric usage, recovered through lexicographic sources, preserves the archaic register of kyanos as ‘steel-blue’ or ‘dark blue,’ a color associated with divine brows, serpents, and deep waters—reinforcing its chthonic and numinous valence. Heidegger, cited by Hillman, pushes the concept furthest: blue is not an image of the holy but is itself the holy, in virtue of its gathering depth. What emerges across these sources is a term that refuses fixity: dark blue is simultaneously a descent into the underworld and the color that initiates the return, the shade of depression and the shade of inspiration, always bearing black within itself.