Did you know you can color the tasks on Gantt chart based on certain conditions?
To create a condition, simply, select the filed, operator and value.
For instance, you want to highlight the tasks that are assigned to a particular resource in purple.
Or, you may want to color the tasks that aren't assigned in orange.
If needed, the created conditions can be edited or deleted.
To prioritize a condition over the others, simply, drag it to the top of the list and save the new order.