You can add a 
		Default Value node to your graph. This way, MyColor provides a default input value, while the user can also provide an alternate input value. If an alternate is provided, it is used. Otherwise, the default value is used. 
	 
Adding the default value nodes to the graph
-  
		   Select 
			 Settings > Toggle Advanced Mode from the ShaderFX menu bar to enable advanced mode. This mode provides a larger selection of nodes. 
		   
- Enter the group view, right-click the work area, and select 
		  Graph Nodes > Code Control > Default Value to create a 
		  Default Value node. 
		
- Connect the nodes as follows: 
		  - Connect the 
				RGB attribute of MyColor to the 
				Default attribute of 
				Default Value. 
			 
- Connect the 
				Alternate attribute of 
				Default Value to the group node. An 
				Alternate 0 port appears automatically. 
			 
- Connect the 
				Result attribute of 
				Default Value to the 
				Value attribute of 
				Multiply. 
			 
 
- (Optional) Create a second 
		  Default Value node and connect it to MyMultiplier as follows: 
		  - Connect the 
				float attribute of MyMultiplier to the 
				Default attribute of 
				Default Value. 
			 
- Connect the 
				Alternate attribute of 
				Default Value to the group node. An 
				Alternate 1 port appears automatically. 
			 
- Connect the 
				Result attribute of 
				Default Value to the 
				Value attribute of 
				Multiply. 
			 
 
Labeling the group node ports
- Select the group node. In the Attribute Editor, make sure that 
		  Active socket 0 is selected, then add 
		  Active socket label MyColor. 
		  The first port of the group node is now renamed to MyColor 0. 
		   
- Repeat for the second port. Use 
		  Active socket 1 with the 
		  Active socket label MyMultiplier. 
		  The second port of the group node is now renamed to MyMultiplier 1. 
		   
Supplying an alternate input value
- Exit the group view and create a 
		  Color node (Hw Shader Nodes > Values > Color). 
		
- Connect the 
		  RGB attribute of the 
		  Color node to the MyColor attribute of the group node. 
		
- This alternate 
		  Color node is used instead of the default value. 
		  
 
		
- (Optional) Repeat for the 
		  Float multiplier. Create a 
		  Float node (Hw Shader Nodes > Values > Float) and connect its 
		  float attribute it to the MyMultiplier port of the group node.