A computational theory of color transparency for color images containing X junctions is described. This theory is based on physical models of color transparency under conditions of additive or subtractive color mixture that describe the relationship among four colors at an X junction. Algorithms are derived for recovering transmittance and surface reflectance functions of a transparent medium from a set of sensor responses at an X junction. The algorithms are based on the ability to describe surface reflectance and transmittance functions by using a linear combination of orthogonal basis functions. We also address algorithms for determination of depth ordering of overlapping surfaces and the type of color mixture by checking the physical realizability of recovered functions.