Remove outline/page border in Microsoft Excel

How do I hide the outside grid lines (at the edges of my data header) in Microsoft Excel?

I need to have gridlines print/view ON for the rest of the data. I can hide some gridlines in my header, by filling the cells with white color, but I cannot get rid of the grid lines on the outside edges (Top Left, Top, Top right). Basically I always have a line/box around my data header.

I have tried changing the line color to white but it does not work. I changed the line color to green. You see a green line on top of a black line.
Any ideas?