We report the self-assembly of disk-shaped molecules that from lyotropic nematic and cholesteric phases in triphenylene-based thermotropic discotic liquid crystalline compounds. A discotic nematic monomer, which exhibits nematic melt at 103 degreesC and isotropization temperature at 180 degreesC, showed room-temperature nematic phase when dissolved in suitable organic solvents at an appropriate concentration. In case of a discotic cholesteric monomer, whose clearing temperature is 190 degreesC, showed cholesteric phase at room temperature cholesteric lyo-mesophase 55 wt% in xylene. The lyo-mesophases of discotic materials, when filled in LC cells, were electrohydrodynamically switchable. We obtained discotic cholesteric films with selective reflected color from an aligned and polymerized cholesteric lyo-discotic system. The temperature dependence of reflection of cholesteric lyo-discotic system was also determined.