Over the years we have seen many techniques and methods in cooking, some are set in stone and others are a matter of opinion. Here is one that I have always questioned; I was taught to never put a lid on green vegetables as it will dull their colour. Now there have been occasions when time was an issue and to beat the clock I have used the forbidden lid and it has not made a difference. I have always found that blanching and shocking in iced water is the best way to preserve the colour of vegetables green or not. Does anyone know the reason behind this method?