I have a pond with a crossover into flooded timber where the beavers are cutting down willows and cottonwoods. The pond has a lodge.

Set yesterday, I caught one young beaver in the pond crossover and had a tripped trap in a dam crossover in the flooded timber.

How many are in a colony typically and how many more should I plan on catching before pulling?

Really depends on how long they've been there. Usually three age classes beaver at most with some exceptions. The breeding pair, last year's kits and this year's. 1-3 beaver is what I'm happy with if I'm not doing nuisance work. Prices being what they are., 2-3 trap checks is all I want to do

Trap them all. It sounds like you have good beaver habitat and if you trap them out more will move In.

Two adults.4 to 6 little ones and maybe a couple 2 year olds depending on age of the beaver house.

On avg,new colony a pair of beaver.
Year two-6 beaver
Year three-10 beaver.Could be as few as 8 or as many as a dozen depending on feed, and predators/trapping.
Most beaver I ever took from 1 colony with two houses was 21 beaver.

probably several more

was the tripped trap a foothold or 330?

If a foothold, make sure to use breasting sticks on the deep water side, this also works at dam break sets.

It was a 330 John.

Reset at night and saw another one swimming in the pond with my flashlight.

Down here its usually 6 to 8 per colony. But as stated above there are several variables: time since occupied; any killed; size of wetland/pond/swamp; unknown/unseen lodges or dens.....