DataTable tableWithColGroup = new DataTable<>("tableWithColGroup", columns,
new SortableContactDataProvider(), 8);
add(tableWithColGroup);
ColGroup colgroup = tableWithColGroup.getColGroup();
colgroup.add(AttributeModifier.append("style", "border: solid 1px green;"));
colgroup.addCol(colgroup.new Col(AttributeModifier.append("style", "background-color: lightblue;")));
colgroup.addCol(colgroup.new Col(AttributeModifier.append("style", "background-color: lightgreen")));
colgroup.addCol(colgroup.new Col(AttributeModifier.append("style", "background-color: pink")));
colgroup.addCol(colgroup.new Col(AttributeModifier.append("style", "background-color: yellow")));
colgroup.addCol(colgroup.new Col(AttributeModifier.append("span", "2"),
AttributeModifier.append("style", "background-color: #CC6633")));
}