I worked on a bunch of 69 340s back in the day. The first 69s I worked on were red. Then the blue ones seemed to be the norm. I did work on a few orange ones later in the year too. I have no idea on change dates or if there even was a relation to date. My guess is they were painted with whatever was available at the time. They probably used up leftover red, switched to blue and when orange was available they used that. I do know that I saw all three colors in 69 cars. The definite majority were blue.