A 10-by-10 grid of dots can be color-coded, with each dot representing one percentage point ... If you need only two colors, be sure to select a pair with plenty of contrast, like a warm and a cool ...

This is shown by the points on the line such as (10, 10) and (-4, -4). Graph A is \(y = -x\). All the coordinates have \(x\) and \(y\) values that are equal in magnitude but with opposite signs.