Photoshop :: Changing Colors Of Rasterized Anti-aliased Text

I have a set of images of complex text that has already been rasterized into pixels. My client would like the images transformed with a different background color and different foreground (text) color.

Just replacing the 2 colors of course does not preserve the antialiasing which provides the smoothness. And when I try hand-editing the aliased pixels it takes forever and always looks pretty bad.

Ideally there would be a way to transform the color schema globally so that the 2 foreground and background colors are changed as directed, and all "intermediate" antialias pixels adjust "accordingly". Does such a transformation exist -- can you specify a color transformation that adjusts 2 colors at once?

Or is there a more painstaking process of masks and such? I've tried several versions with masks, selects, feathering etc. but haven't found anything yet that gives professional antialias quality to the final recolored result.