75 Ohm trace with error markers in Altium
Are you sure it's a violation marker? Those default to bright green. What you have could just be display override color for that net's connections. 

Is the * column for the net checked in the PCB control pane, like this one?



Un-check your net and it should then only color ratsnest wires and not all objects tied to that net.

Edit: clicking around a bit more it looks like this feature is called "display override" in case you want to search for it on the Altium Wiki.