For SESI I'm going to setup a colour guide for nodes, a guide you can refer to if you wonder which colours you're suppose to use. Since this isn't really defined, I wonder: What colours do you use?
To give an head start, these are the colours that I use:
VOP's
Outputs data: Green (second column)
Imports attributes: Purple (second column)
Parameter controlled by user: Yellow (fifth column)
DOP's
Merge nodes: Gray (Second column) doesn't add or directly modify any data
Switch solvers: Gr