According to the agent I talk to, the rain fabric is water proof, so it doesn't let the water go in; but honestly, I've never work with this fabric; so all information I'm giving you is based on their information.

what color are the cushions? are the chairs black resin or brown? Do the cushion covers zip off for cleaning? how do you care for?

As described, cushion color we call it Ivory; which is off white, all appeared so can be removed and machine washed, delicates cycle, cold water, air dried, do not use dryer; wicker color is espresso which is a very dark chocolate brown (see close up attached)