Here is a survivor car that can be used as a reference. I've got a pair of valve covers from a '69 340 that are "Turquoise" and a pair of valve covers off a '73 that are blue. They were both taken off and put on the shelf in my Dad's garage early in the cars lives so neither should have faded much. The '69 covers are blue (like the blue in the article) but when compared to the '73 blue they are obviously a lighter color, but it would be a stretch to call them turquoise.
http://www.moparaction.com/Article/JUNE/JUNE.html