Magenta line
I recall, many years ago, conducting what is now called an SEP renewal for a 757 skipper who was on layover in USA.
I gave him a 'half mill' chart and asked for a VFR cross country to a nearby airfield. He elected to "busk it" (no planning).
On the downwind leg from the departure airfield he gave me the aircraft back - admitting that he "hadn't a clue" and without his magenta line and glass flight panel he was completely stuffed.
Gave him quite an uncomfortable wake up call, he said.