I really think it depends on the colors and hues in your kilt. You want to go with something that will accent and enhance your kilt without over stating it. I personally am not a fan of the white hose as an end all to some idea of "dressy". I think that Lovat green looks very good, dress or casual with my Ancient Grant tartan. Several colors will go with just about anything and may be more appropriate for casual such as the Oatmeal colors and greys. As MbHandyfound out , try a color or two, or if you can take the kilt or a swatch and compare it to colors available and see what strikes your fancy and looks dressy.