I use white for temporary lines - it is great for reclaimed, hewn, or rough sawn where you can't leave the line and you can't plane it off. Sometimes it is a little too temporary -- you may need to resnap a few lines that disappear too soon, but that's what you want anyway.
If I was really concerned with having an extremely fine line that was invisible after assembly I'd do the stretched cord thing and sketch it on with my Hock Layout knife.
It's also what I use to layout lines someone else will be cutting.