My largest colony is 4 females, 1 male. Generally though I just do trios. I'm not sure of the exact measurements, but my large colonies are in cages where the jump cover has been removed in the middle. If I had to guesstimate, I'd say 48 wide by 20 tall by 28 deep. Trios would be half of that. I would provide slightly larger cages if I had room, but not much larger as then I would be worried about kits falling, mom getting too high for the kits to reach, etc.
There are a lot of threads on the forum about colony breeding. If you use the search function at the top of the page, type in colony, you can read through all of them rather than having people re-post the same information. If you don't find what you want in there, then post the question and we can answer for you.