Upvote:2
It's possible I misunderstood what the Wikipedia article said: according to a google book search, the True Whig Party was the political organisation of dark-skinned Americo-Liberians, who were believed to be of 100% African ancestry.
It seems the Republican Party was the party of light-skinned, apparently mixed race Americo-Liberians, who were called mullato people at the time.
The source is below, any other information would be welcome.