The background color of a contextual tab depends on the type of task being performed.
Object Select Contextual Tabs (Green)
Contextual tabs that are displayed when you select an object have a green background color. For example, if you select an assembly object, the Assembly contextual tab is displayed. That tab is displayed with a green background color.
The following illustration shows the assembly object select contextual tab.
Non-object Select Contextual Tabs (Purple)
Contextual tabs that are displayed when no objects are selected have a purple background color. For example, if you click the Assembly button 
on the Modify tab, the Assembly non-object select contextual tab displays, and that tab has a purple background color. This provides access to all commands related to assemblies without having to select an assembly in the drawing.
The following illustration shows an example of a contextual tab that is displayed when no objects are selected.
Non-object selection contextual tabs have a Close button at the end to dismiss them. If you select an object while this tab is displayed, the non-object selection tab is automatically closed and replaced with the object select contextual tab.
Section Editor Tab (Blue)
Because its ribbon behavior is slightly different than the previous two types just described, the Section Editor tab has its own unique background color — blue.
