achromatic

1. Designating color perceived to have zero saturation and therefore no hue, such as neutral grays, white, or black.
2. Refracting light without spectral color separation.
3. Biology. Difficult to stain with standard dyes. Used in reference to cells or tissues.
4. Music. Having only the diatonic tones of the scale.

[From Greek akhrōmatos : a-, without; see a-¹ + khrōma, khrōmat-, color.]

Said of architecture that is without color, for example, the white buildings of Greek Revival.

The quality or the condition of being achromatic; staining with difficulty.

See diatonic.