I had a guy come in to do some drywall taping today and I had a bag of 20 min hot mud and a bucket of each green (regular) and blue (lightweight) joint compound. I always though that the green should be used for the first two coats cause it is stronger and blue for the final coat cause it is easier to sand.
Once the dude finished the bag of hot mud, he went straight for the blue to do a little bit of first coating that was left at the end of the day. I asked him why not use the green and he said they were the same. I was not really sure in my assumption stated above and was tired at the end of the day to argue and also I wanted to trust his experience so I just let him do a couple of panels and a joint with the blue.
Who is correct, me or him?
If I am right and he is wrong, why could have led him to fail at differentiating?
If I am wrong and if they are indeed the same, why would they even have two different products (by the same brand)?