An illumination source including a first OLED layer capable of emitting light of a first color, a second OLED layer capable of emitting light of a second color and disposed on the first OLED layer, each of said first, second OLED layers including alternating active light-emitting areas and inactive non-light emitting areas; said first OLED layer comprising a first substrate, a first transparent electrode layer disposed on the substrate, a first electroluminescent layer capable of emitting light of the first color disposed on the first transparent electrode layer, and a first patterned metallized electrode layer forming the alternating active light-emitting areas and inactive non-light emitting areas; and said second OLED layer comprising a second substrate, a second transparent electrode layer disposed on the substrate, a second electroluminescent layer capable of emitting light of the second color disposed on the second transparent electrode layer, and a second patterned metallized electrode layer forming the alternating active light-emitting areas and inactive non-light emitting areas; wherein light emitted by the active light-emitting areas of the first OLED layer is transmitted through the inactive non-light emitting areas of the second OLED layer. A method for tuning color and/or intensity of the light output of an illumination source is also disclosed.