Different colors for labels when completed is checked

[nafergo]

A color for "completed" status tasks would allow for easier overview between completed and todo tasks. Right now, the process is to activate custom colors for nodes and then apply to the node. That's actually not bad because other color-status code can be created but:

• new node tree means recreating the color scheme (or append a node tree with nodes that use the color scheme from other blend file)
• the custom color changes the color of the background for the all node... in my opinion that ends up being too much. Changing the color of the label (like the compositor uses to make it clear the different types of nodes) would be great.