Colder air means denser air, since the air molecules jiggle around less. If the air is denser then the speed of sound becomes larger, I think. Well the speed of sound will change depending upon the density of the air. On the other hand, the length of the pipe will not change appreciably. So you may assume the length of the pipe is fixed, which means the wavelength of the sound produced is fixed. The frequency, or pitch, of the sound is related to the speed of sound and the wavelength by the dispersion relation:
(speed of sound) = (frequency of sound)*(wavelength of sound)
depending upon whether the pipe has one open end or two open ends, I believe that you should find the answer.