The coloration phenomena of porous poly(vinyl alcohol) (PVA)-poly(vinyl acetate) (PVAc) composite films in organic solvents, which were prepared from dried PVAc latex films containing PVA as a protective colloid with acetone extraction, have been investigated from the standpoint of light dispersive power. When the white opaque porous films were dipped in organic solvents having a refractive index near that of PVA, they became so transparent that one could read letters under the films. If solvents having a high light dispersive power such as aromatic compounds were used, the porous films became markedly colored. The color of the scattered light, which was complementary to that of the transmitted light, did not change with the observing direction (v s) the irradiating direction of the white light and shifted from yellow to green through orange, red, violet, and blue as the refractive index of the solvents increased. This was evident from the fact that the intersection of the dispersion curves of PVA had a low light dispersive power and solvents had a high light dispersive power. The coloration of the porous PVA-PVAc composite films in the solvents showed reversible thermochromism. The residual grafted or highly branched PVAc in the spherical cells of PVA after acetone extraction played an important role in the penetration of solvents into the inner parts of the porous films and in the refractive index of the PVAc swollen by the solutions in the porous films. (1994 Academic Press, Inc.