I have been using Rain-X orange colored wiper fluid for the last couple of years, year round, and it is by far the best wiper fluid I have ever used. It improves the visibility through the windshield like a treatment of Rain-X would and It has never frozen in the tank or even on the windshield when driving down the highway in sub-zero weather.
I thought that I would share this with people as I have seen a few questions asked about wiper fluid on the board lately. It used to be around $5 a jug but I saw at NAPA that it is now down to $2.xx and the guy there said it is even cheaper at Walmart.
I saw a guy at the gas station this morning buying a jug of the blue stuff they sold there and had to shake my head as the gas station had filled up their window cleaning tubs, by the pumps, with the same stuff and it had all frozen. I assume that it is not very environmentally friendly, yet probably better than getting in a wreck and causing all types of fluids and materials to get all over the ground.
Drive safe...