I just finished repairing the genoa. Last year the straps that hold the ring ripped from chafing. The only color the store had was green. If the sail wasn't on its last legs I would have found some white somewhere. As it turns out having the tack green made set up very easy. I will color code the tack and head of all my sails in the future.
At the end of the season the sail ripped about a foot up the tack. The material is thin and weak from sun exposure. Cut some cloth from an old sail and laminated the sail between two pieces of this cloth. Hope it holds one more season. Next winter I plan on making a junk sail like Phil has on his Brenda B.
I used red thread because that's what I have. It's for another sail project I have converting a Mirror dinghy to a junk rig. It's best to start small and practice.