The use of high reflectance aluminum lighting guides is most frequently used material for actual natural lighting systems. Spectral Reflectance over the entire length of a light guide changes the color of the output light at the end of the guide. When light guides are made of a prismatic film, the influence of the reflectance is minimizing and absortance is not important when the sheets are thin. Color Rendering index and color temperature will be important parameters in order to evaluate Lighting quality and therefore in Museums, office buildings and production centers to get the normative approval. In this paper a theoretical simulation and 3D ray tracing for aluminum and prismatic light guides of different shapes (rectangular and cylindrical) and lengths over the entire visible spectrum are studied. Output light color temperature related to several illuminants and CRI are evaluated for the simulated aluminum and prismatic light guides. Thus, prismatic light guides seem more robust in lighting quality maintenance regardless of conditionals like angle acceptance for TIR guiding, aluminum guides are efficient and maintain light quality only for short distances.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.