  We propose a new method for the classification of optically dark gamma-ray
bursts (GRBs), based on the X-ray and optical-to-X-ray spectral indices of GRB
afterglows, and utilizing the spectral capabilities of Swift. This method
depends less on model assumptions than previous methods, and can be used as a
quick diagnostic tool to identify optically sub-luminous bursts. With this
method we can also find GRBs that are extremely bright at optical wavelengths.
We show that the previously suggested correlation between the optical darkness
and the X-ray/gamma-ray brightness is merely an observational selection effect.
