There doesn't seem to be a consistent policy about the replacing of ponchos. I doubt they would replace the discolored one unless you just happened upon a super nice CM. The one with the hole, they might.
A couple years ago I somehow ripped by Disney poncho down the side while it was pouring rain. I wasn't even thinking about a replacement since the poncho was several years old. I went into a gift shop and asked if I could use their stapler and was going to attempt to staple up the rip. The CM was very nice, threw away my ripped one and gave me a new one.