I'm glad it's not just me who suffers from foot-in-mouth disease. I still blush horribly when I think of the following faux pas.

I worked with a guy who kept a picture of his wife on his desk. She was quite large and blonde. Years later, I met him and his current wife (a slim rehead) at a social function. Later on in the ladies' room, we were chatting. "Oh, you must be his second wife" I said. "No", she replied "his first and only wife". And before I could stop myself, I blurted out "You can't be. She was big and blonde". She laughed and said "Yes that was me". Needless to say, she had dyed her hair and lost heaps of weight. Fortunately, she regarded it as a compliment but I could have bitten my tongue.