I don't know if 1969 340 engines were blue, orange or turquoise. However, one point of clarification: the proper Chrysler engine green/turquoise is Dupli-Color DE1619. Dupli-Color calls it "Chrysler green engine enamel". (I used the color on my 440.)
The internet ad pictures for this product are often misleading and confusing because they incorrectly depict a generic blue rather than the Chrysler green.
Here's a picture of one of my cans of DE1619. In person it is somewhat more green than even this picture suggests.