Damask designs are a difference in how light is reflected in certain areas due to a different weave pattern. This means the designs aren't always glaring you in the face, but instead are an subtle accent. This is especially true with the white option.
The Colmcille design, named after the one of the Irish Patron Saint, is a border of Irish Knotwork. One of the many interpretations of this design, is that it's an expression of the repeated crossing of the spiritual and physical paths in our lives.