I think you are still confused about the color, the first response appears to be an original paint Y3 '69 Belvedere (I know it's not a Road Runner ), "mustard" has NOTHING to do with it. Pics of a correctly restored Y3 anything is a tall order (see '70 R/T pic) - few would go thru the "hassle" for such a bland low-impact color.

1968 "H" - 1969 "Y3" - 1970 "DY3" are all the same color

Chrysler "antique ivory" - Dodge "cream" & "light gold" - Imperial "champagne" - Plymouth "yellow gold" are all the same color

Here's the '70 Duster in DY3 Yellow Gold...same color as Y3 in 1969

On second look I believe you're right. The ad says it's Yellow Gold, hence my thoughts on it possibly being Y3.

maybe it was "yellow gold"?
are those original paint "Y3" spots showing thru a decades old "Bahama yellow" repaint

I have no doubts this color is the rarest of the factory offerings for Plymouth Road Runners in 1969. Very scarce animals.

Ah hah! Found one!! The color looks off though.
http://www.moparsonsale.com/mopars-for-sale/l0217.php

Another.
http://usedcarsfsbo.com/asp/Item.asp?soldid=45114&make=Plymouth&theday=2%2F12%2F2012

Anybody know anyone with a Road Runner in this color?