Graphical Indicators with Custom Fields - Microsoft Project Server 2013 | Microsoft Project Online
Microsoft Project Server/Online facilitates with several custom fields that a user can define and use to meet their organization's needs. You can create new custom fields that full fill your specific requirement, customize an existing field and then insert it into your project, or you can also simply rename existing fields to customize them.
Enterprise Custom Fields includes different sets of variables, option of inserting custom formulas, can use lookup tables (as defined by user) and graphical indicators to add look & feel to a value. In example below I have done same thing, I have used the Project Percentage Completion value & by using graphical indicators i have added some colors to a number value.