I don't think you can change the gridlines, but you can choose whether or not to print them, and whether or not to display them.
You can change the cell border colors, and cell background colors which, will make it appear as if the gridlines are colored. This is done by selecting the cells, right click and select Format Cells, and then on the Border and Fill tabs, changing properties. So, make the Fill Black, and the Borders white.
If you select the View tab, you can choose to have gridlines not display, giving a blank sheet a pure white background. Te absence of gridlines won't impact the Cell Border colors.