Is it possible to give a subsystem different outline colors (foreground color different for each port)

Hello everyone, I just wanted to know, whether it is possible to give a subsystem different outline colors. I know I can change the foreground color of each outport-block in a subsystem, so the port label will change its color to.

Then it Looks like:

But how can I get the signal color of "out (kg/s)" red?