Abstract: A photochromic photo resist composition that changes color on exposure to radiation; thereby providing a distinctive visible interface between exposed and non-exposed areas. In the composition, 0.2-5% of a photochromic dye solution is prepared in hot toluene. Twenty parts of the dye solution is then added slowly to the photo resist under mild agitation, thereby forming the color changing photo resist. The color changing property of the photo resist facilitates alignment of mask patterns in continuous patterning of images on a large substrate.