STEP 1: Make cell B2 the active cell. Right-button mouse click cell B2 and select Format Cells from mouse shortcut menu.

STEP 2: (FIGURE 1) Let’s begin with the Line style section. The style we want to select is the second one from the bottom (of the right column – it’s a solid, thick line).

STEP 3: Select the red color from the Color drop-down arrow. Notice that when you do, all of the line styles change to that red color, as shown on the right.

STEP 4: In the Presets section, select Outline. Notice that you see a red outline image below (FIGURE 2).

STEP 5: ​Select OK. The cell has a red border now (You must click on another cell to see the red border outline) (FIGURE 3).

STEP 6: This border process can be done to a range of cells also. Highlight cells D2:F4. Right-button mouse click any part of the highlighted cells; select Format Cells from the shortcut menu.

STEP 7:  Select the same line style and red color as we did in previous example (FIGURE 4). 

STEP 8: Select Outline, then select Inside (FIGURE 5). You now will see your highlighted cells with a red border on the outside as well as between cells.

STEP 9: Notice that in the Border section, there are other border options (FIGURE 6). You can choose to put a border on any side of a cell(s) by selecting the appropriate icon.