The red light means a failed download. You can try it again if you want, also you can delete it directly.
The second light means the task is connecting.
The clock light means this task is a scheduler task, it will be downloaded in time you have setted.
The blue light means a pausing task, you can start it or delete it.
The green light means a downloading task, you can pause it or delete it.
And the last light means the task is in waiting list.