I map the colors based on the color values of the Fill (#EBEB3F) and Outline (#101010) - same colors as the PNG. The background color defaults to #000000 black so I leave it at that. I've tried other colors for the background and it just imports as a huge black frame with the yellow text still looking crusty.
Here's the two Color Mapping windows: http://creativelybankrupt.com/encore/mapping.jpg
And this is the Timeline default colorset: http://creativelybankrupt.com/encore/colorSet.jpg - I've tried with and without antialiasing based on the Fill/Stroke. Same results.
The PNG files have no aliasing and it is a solid one-color yellow with a one-color dark stroke. When imported and viewed in Encore, it is as if the stroke has been eaten away, as shown in the linked image from my original post.