Hi @Marcia562,

Here is a revised version that will have activities that start in the next 10 days turn green:

=IF([% Complete]@row = 1, "Blue", IF([End Date]@row < TODAY(), "Red", IF(AND([Start Date]@row <= TODAY(), ABS(NETWORKDAYS(TODAY(), [Start Date]@row) + 1) / ABS(NETWORKDAYS([Start Date]@row, [End Date]@row)) > [% Complete]@row), "Yellow", IF(AND([Start Date]@row <= TODAY(), ABS(NETWORKDAYS(TODAY(), [Start Date]@row) + 1) / ABS(NETWORKDAYS([Start Date]@row, [End Date]@row)) <= [% Complete]@row), "Green", IF(AND([Start Date]@row > TODAY(), [Start Date]@row <= WORKDAY(TODAY(), 10)), "Green", "")))))

For best practices, please reference Advanced Formula Examples sheet in the Smartsheet Formula Examples Template (Smartsheet Formula Examples Template | Smartsheet).