mybe this wil help it -The cloud detection : how it works (Venµs)
for the start i thinek WorldView-2 have blue band
The basic technique consists in thresholding the image of a spectral band in the short wavelength range (preferably a blue band). Pixels whose reflectance is above the threshold are declared cloudy
http://www.cesbio.ups-tlse.fr/multitemp/?p=876