A key assembly for an electronic device that includes a keycap defining a key that has a non-opaque portion to identify the key that is backlit. The assembly includes a light guide positioned in spaced relation to the keycap. An optical radiation source, such as top-fire light emitting diode, is mounted below the lower surface of the light guide. A mask is disposed on the top surface of the optical radiation source. The mask includes an aperture to allow light from the optical radiation source to pass into the light guide, and the mask blocks at least a portion of the light from the optical radiation source. The mask blocks a portion of the top surface of the optical radiation source that emits tinted light. The light guide is affixed atop the opaque mask such that it is nearly directly affixed to the optical radiation source.