Create Percent Bars to see numeric data as bar, where the cell is filled as a % of its value against the maximum value for the column.
Percent Bars work for both positive and negative values and you can choose whether to display the actual value. If the column is editable, then you can still edit it as normal.
In this example we created 3 Percent Bars. The 'Change Last Order' Percent Bar automatically shows the negative values, while the 'Item Cost' one displays cell values as well as uses a non default colour.