I'm glad someone mentioned this, because I've been wondering about it too. I get natural gray on the sides, quite a bit actually...but I am not ready to start ordering TL pieces with gray mixed in. Maybe when I'm in my 40s.
I guess all I can do is use something like Just For Men on the sides. Its just worrisome that the color on the sides and the color of the piece might be different.
-On the other hand, "because I color out the gray" can always be my excuse if someone is wondering why they are different shades.