isochromatic

American Heritage® Dictionary of the English Language, Fourth Edition

1. adj. Having the same color or wavelength. Used of light.
2. adj. Orthochromatic.

Century Dictionary and Cyclopedia

1. Having the same color: said of the two series of oval curves of the interference figures of biaxial crystals. Each curve in the one series has one corresponding to it both in form and color in the other. The two curves or lines that have the same tint are called isochromatic lines. See interference figures, under interference, 5.
2. In phytog., same as orthochromatic.

Wiktionary

1. adj. optics Having the same colour or wavelength.
2. adj. Of or corresponding to constant colour.
3. adj. Of uniform colour.

GNU Webster's 1913

1. adj. (Opt.) Having the same color; connecting parts having the same color, as lines drawn through certain points in experiments on the chromatic effects of polarized light in crystals.