Add 1 1/2 cups boiling water to each package of Jell-o in separate bowls. Mix Knox into 1/2 cup cold water – let sit.
Scald the milk and then remove from heat. Add sugar and vanilla to milk. Add sour cream and vanilla. (I use a mixer to blend it all together to avoid lumps).
Pour 1 layer of Jell-o in 9×13 pan (clear glass one looks best – you can see colors through – but not necessary). Put pan in refrigerator and let set up completely.
Then pour one layer of white sauce (1 cup) and put in fridge. Alternate color and then white sauce. Make sure each layer has set up before adding next layer. You will end up with a layer of white on top BUT I have on occasion, used more than 1 cup of white and end up with a color on top. I usually top it with whipped cream anyway.
This recipe takes a long time but not much work — you just need to find something to do in between layers. Each layer takes approximately 1/2 hour to set up but as you proceed, they take a little less.