Guess you and I were the targets of the Rain Gods today, Lindsay. We were on our way to Home Depot when the skies opened twice for about 4 minutes each. Once when we were getting into the car and the other time when we were coming out of the store. Must be thankful for every drop of rain at this time of year. Never know when you'll get some more. Do you have any rain catchments set up?
I do see that reddish color come and go on my orchids at times, most of the time it's nothing to worry about as Ursula says. It just seems to fade out again. But if there's any red on the leaves, then I make sure to give that orchid an extra dose of Epsom Salts. I've even let one soak in a bucket of mild Epsom Salts when too much red turned up at once. It fades out in less than a week if you do that.
My automatic sprinklers, and the mist system in the cage both spray high pH well water, so I really watch now for that red color to show up. It means the phosphorus in the well water is preventing the uptake of minerals. I've seen a lot of improved growth this year since I adjusted my water and fert regime.