changed colour of nodes with unknown output types from white

The default colour for nodes with unknown output types is white which makes the node name very hard to read, so i changed it to a dark green. feel free to change it to any other colour as long as its easily readable
change default colour of nodes with custom outputs

decided not to change the name DEFAULT_PORT_COLOR to DEFAULT_NODE_COLOR because then it is unclear it is related to PORT_COLORS.
Merge pull request #371 from derpDiggler/patch-2

changed colour of nodes with unknown output types from white