  We describe a technique that uses radial color gradients in disk galaxies to
detect the presence of bulk non-circular motion or elliptical orbits. In a disk
galaxy with both a radial color gradient and non-circular motion, isochromes or
iso-color contours should follow the shape of closed stellar orbits, and the
ellipticity of the isophotes should vary as a function of wavelength. A
difference in the ellipticity of isochromes and the isophotes can be used to
detect the presence of non-circular motion. A model galaxy is constructed which
demonstrates this phenomenon. The difference between isochrome and isophote
ellipticity is directly related to the ellipticity of the potential. This
provides a new way to measure the ellipticity of the dark matter in the outer
parts of galaxies.
  As an example, we apply this technique to two dwarf galaxies NGC 1800 and NGC
7764. We detect a bar in NGC 1800 which has only previously been suggested from
the HI velocity field. In NGC 7764 there is no color gradient along its bar so
we cannot detect non-circular motion in this region; however ellipticities
observed in a star forming ring at the end of the bar are consistent with this
ring being located near the corotation resonance.
