Colonizing Io would have numerous challenges. Due to high volcanism( due to Jupiter and Europa's tug of war force) and high radiation levels( due to Jupiter's radiation belt), the only way to make colonization of Io possible, is to move its orbit over to rotate around Venus (why necessarily Venus? Elsewhere is also possible, altough Venus is also possible). Not just to create tides( depending if the planet Venus is terraformed) but also this would reduce volcanism on Io and radiation levels will reduce. However, there would be solar flares but if inhabitants live in biosphere habitats that will shield them from solar flares. However, another possible way of colonizing Io is by establishing underground bases. but not be close to a volcano. This would be an easy way to colonize Io but until further notice, colonizing Io would require technology far beyond our level.