I don't use any colored fuel lines because it makes it much harder to see air bubbles in the fuel, I just but it in 10' lengths and replace it as soon as I detect the open end that hooks up to the card, getting stiff, it becomes another place for potential air leaks.
In 2001, I bought a spool of .25in Tygon. We got out of karting in 2003. Since then I been using the Tygon for mowers and other 4cycle small engine equip.
Just checked..........the Tygon spool hangs on a wall in the unheated wash room........it is still pliable and ready to use next Spring if needed. I have one mower that I replaced the fuel line with Tygon in 2006, and have cleaned the carb each Spring since then, and the Tygon fuel line is still good. Great stuff.