Constrain connections between ports?

[RThomasHyde]

Is it possible to specify that certain input ports can connect only to certain output ports (and vice versa)? For example, if I had "red" and "green" output ports, and also "red" and "green" input ports, is it possible to only allow a connection dragged from the "red" output to attach to a "red" input port? Also, is there a way to provide feedback when dragging a connection over a port, e.g. to indicate that the connection is allowed/disallowed?