= Solution
The first zero of each colour is at $\theta=\lambda/a$. Blue therefore reaches its first zero closer to the axis than the reference green <wavelength>, and red reaches it farther away. At $\theta=\lambda_0/a$ the reference colour is absent, while other <wavelengths> remain: \b[there is no common black first minimum in white <light>]. Adjacent regions change hue as different colour minima pass through them; <wavelengths> longer than the reference are still in their central maxima and tend to dominate near its first zero. The exact hue depends on the incident spectrum and spectral response.
Back to article page
