In this study, we explore a relation between reflection colors and a chiral concentration. Basing on our observation, the reflection colors in BPI are dominated by lattice surface of the platelets and the lattice constant of a unit cell, but they do not depend linearly on the chiral concentration. The reflection peak moves to a short wavelength as increasing the chiral concentration because of contracting the lattice constant. However, when the lattice plane is changed, the reflection is dominated by the lattice plane, and it may move to a longer wavelength.