[Video:
http://www.youtube.com/watch?v=FpOYuCn95dY]
66S:
http://www.philcoradio.com/gallery/1935c.htm#n
You will note the area surrounding the grille, escutcheon and tuning knob is somewhat darker than Perfect Brown, but not as dark as Extra Dark Walnut. Several coats of Perfect Brown might replicate this color. Since Ultra Classic is dye-based instead of pigment based, you won't have to worry about multiple coats turning into paint (hiding the woodgrain).
Remainder of front panel: Medium Walnut (what is the Ultra Classic equivalent of Medium Walnut Tone Finish, anyway?)
Top, sides and trim: Extra Dark Walnut Ultra Classic, sparingly applied.
Now, I've seen some 66S sets that only had the dark walnut on the trim, and Medium Walnut on the side panels. I haven't seen enough original cabinets to establish which is correct (or if both are correct). Most of the 66S cabinets I have seen were stripped and refinished in a single Medium Walnut color.
80 Jr.:
http://www.philcoradio.com/gallery/1933a.htm#h (link goes to an 81 Jr., same colors)
Outer edges of front panel and sides: Perfect Brown, multiple coats as above to achieve a fairly dark finish that is not as dark as Extra Dark Walnut.
Bottom trim: Extra Dark Walnut
Inner front panel: I'm not sure about this. After studying several of these, I have to disagree with my previous comments in the link which Bob (klondike98 ) was kind enough to post above. It has to be something lighter than Medium Walnut...but I don't really know which shade. I think Light Fruitwood might be too light (tried it once, was not happy with the result). But Medium Walnut is too dark.
