There have been a few experiments into the natural circadian rhythms of humans and it seems that we seem to be have an inbuilt clock which is just slightly over 24 hours.See experiments here.
I imagine that, like with the experiments, that the new colonists could just use lighting to keep themselves in a 24 hour(ish) rhythm in their sleeping quarters. The only issue would be with with outside work, but they could just use portable lighting during dark periods. Humans survive harsh conditions like working night shifts, living at research stations near the North Pole (where days and nights can be long), and even on the International Space Station, and just adjust to it thanks to electric lights.
A bigger issue would be growing plants outside, which also seem to have a similar 24 hour rhythm. They may adapt to a planet with a short day/night cycle, but may be killed off if the planet has an extremely long night period, as they would not be able to photosynthesize until it is day again. While you could again get round this with hydroponics and UV lights, it may not be practical for a large scale colony.