One of the persistent themes in Wittgenstein's philosophy is the concept of color. It is evident that Wittgenstein takes up the problem of color from his early period on. He mentions color only a few times in the Tractatus, but with very important ideas in his phenomenology. He not only introduces the concept of color-space,¹ which consistently continues to appear in his later writings about color concepts, but treats color as one of the forms of objects.² The introduction of color-space that cannot be separately understood without reference to visual space suggests Wittgenstein's concern is not with physical colors but phenomenological colors from the initial stage of his philosophy.