LOTG does actually mandate a coin toss (and from this season the referee has to toss the coin). That being said, I can't see that being top of anyone's moan list in a grassroots game.I've never taken a coin out with me.
This was an accident on my first game (i forgot a coin) so i decided to say to the away captain "red or yellow".
And in my left shorts pocket i have one of each (for 2 yellow card dismissals).
Nearly 30 years later i've never changed.
I've saved myself a few quid in the process!!
I don't think I've ever done it in an 11-a-side game, but I have certainly done the 'which hand is the grass in' trick in small-sided tournaments where I have lost my coin and not had time to go and get another one.