Webb can see in the visible light range, but is optimized for infrared observations. Like you mentioned, distant galaxies can be so redshifted they are only visible in IR. This is especially true of some of the earliest galaxies formed after the Big Bang, which is one of the types of objects Webb is primarily aimed at studying. Astronomers hope that Webb will allow us to understand our early universe, as well as galaxy formation by allowing us to see all stages of the process!