You can send us pictures and files here: svetoslav@jqwidgets.com
To match the background of the checkbox column with the other columns you can do the following:
In an onCellRender callback, you can select every smart-grid-cell with an attribute header.
Then remove the attributes ‘header’, ‘freeze’ and set the ‘role’ attribute to ‘gridcell’.

Here is an example of this: https://codepen.io/dkeamcaksoem/pen/eYrXOEP

To remove the column header lines, you can set the ‘showColumnHeaderLines’ of the ‘appearance’ object to the grid.
This is also shown in the above example.

Hope this help, if not, do not hesitate to contact us!

Best Regards,
Svetoslav Borislavov

Smart UI Team