What was once called blending inheritance, or incomplete dominance is now known as codominance. Neither red nor white colour is dominant and therefore the result is a blend. Be careful now. Partial dominance, i think, is when both alleles are expressed in the organism but they are not blended. Such as the example given earlier with a pure black cow mating with a pure white cow giving a white cow with black spots.
Continuous variation is a completely different thing.
This term only indicates that a certain trait has polygenes, or multiple genes, which is expressed in a wide variety of characteristics.