I think the adaptive subdivision does not gives enough geometry to do the displacement accurately. If I actually subdivide the plane with 6 subdivision and apply it then I add to it another 5 simple subdivisions (not the adaptive one), so overall I got around 4 million faces to play with the mud displacement and the color are in sync.
IMHO In Eevee there is no displacement so that is the reason why the material works perfectly there. And also I guess setting the viewport dicing value to 1 px helped too.