Draw 15 evenly-spaced vertical lines on a piece of paper to make the columns for your chart. Make each column wide enough to accommodate a two-digit number, plus its sign.
Draw 15 evenly-spaced horizontal lines on top of the vertical lines to create a grid.
Write the numbers zero through 12 in permanent marker across the first row and down the first column, one number per box.
Subtract each number in the top row from each number in the left column and write the answer in the box formed by the intersection of appropriate row and column. Write positive numbers in black ink and negative numbers in red ink.
Shade the boxes that have negative numbers with the red colored pencil, then shade those that have positive numbers with the blue pencil. Leave all the boxes with the number zero white.