Click the + next to the your chart expression (in the Properties | Expression dialog), and then enter the condition in the Text Color box. You would need something like:
If(Sum(hours) = 0, LightGray(), If(Sum(hours) < MinimumHours, LightRed()))
Where MinimumHours is the staff member's minimum daily hours.
To set the header to display in blue, you will need to use custom formats.To set a custom format, turn on the design grid (View | Design Grid). Then right click on the header line and select Custom Format Cell.