Content space for bx--col-xs-12 bx--col-sm-6

Full space for bx--col-xs-12 bx--col-sm-6 (columns naturally have padding on them, adding a background color to the column directly will effect the entire column, as opposed to using a child element in the example to the left).

Columns also expand to match the vertical size of the rest of the row (see red column)

Background color over entire column, not just content space

This content is offset. Offset adds a left-margin for x columns.