An illumination device for simulating neon or similar lighting is generally comprised of a rod-like member, a housing, a light source, and an intermediate light-transmitting medium extending along and positioned adjacent the light source with a light-receiving surface for receiving light emitted from said light source and a light-emitting surface for emitting light into the rod-like member. This intermediate light-transmitting medium is preferably composed of a matrix of a substantially translucent acrylic, polyurethane, or similar material tinted with a predetermined combination of one or more fluorescent and/or phosphorescent dyes. The intermediate light-transmitting medium is subdivided into independent sections, each of which is provided with differing combinations of fluorescent dye, phosphorescent dye, and/or no dye at all.