This article focuses on an innovative one-pot fabrication of organic/inorganic hybrid parallepipedic tubes with rectangular cavities displaying multicolor luminescence. Firstly, using a novel back-to-back coupled 2,6-di-pyrazol-1-ylpyridine ligand, blue-emitting several-micrometer-long (ca. 50 μm) parallepipedic organic nanotubes with rectangular cavities were fabricated in THF/water via supramolecular (H-bonding and π–π stacking) and solvent-assisted self-assembly. Secondly, in the same pot, the ligand molecules available on the surface of the ligand nanotubes were reacted with Eu(tta)3 molecules at the solid/liquid interface to form a layer of red-emitting Eu(III) complex coating on the inner and outer surface of the tubes. The resultant organic/inorganic hybrid parallepipedic nanotubes fabricated using this novel bottom-up one-pot technique display tricolor (blue–red–purple) luminescence, i.e., blue and red dual emission from the organic ligand and the Eu(III) complex, respectively, and a purple color due to the mixing of the two colors. This simple technique signifies an innovative and important method in the development of bottom-up nanotechnology of multiluminescent organic/inorganic hybrid nanotubes.