Both are light colored, and the pleochroism of the hypersthene is sometimes quite faint.
The mineral is a low-grade metamorphic amphibole characterized by pleochroism in shades of blue and violet.
In addition to color, a grain should be checked for pleochroism using polarized light.
British Dictionary definitions for pleochroism
a property of certain crystals of absorbing light to an extent that depends on the orientation of the electric vector of the light with respect to the optic axes of the crystal. The effect occurs in uniaxial crystals (dichroism) and esp in biaxial crystals (trichroism)
pleochroic (ˌpliːəˈkrəʊɪk) adjective
C19: pleo- + -chroism, from Greek khrōs skin colour