I'm not going grey myself...but based on what I've seen on others, I think that simplest and most graceful way is just to decide not to color when grays appear. They will know, where to come, and in my opinion, salt and pepper look is quite attractive if the hair is healthy.

From experience, however, I can tell, that treating your hair gently and giving it what it needs and no more, will give it great shine too.  I'm an ex shine spray user: I liked to spray it sometimes just to get a little "extra" shine. After three months here, I gave it away as obsolete, along with my commercial styling products. 

Never coloring your hair is the "best" way to allow yourself to go grey gracefully. 

However, if you really feel you much color, try to keep your color within 3 shades of your natural color.  As the amount of grey/silver increases, you may need to change the shade a bit.  Using henna might be a better route, if you have darker hair to begin with.  The color will just fade out and be less noticable than with a permanent color.

When the time comes that you decide to quit coloring, you will want to try to have your color as close to your natural color as possible.  Sometimes having low-lights will help with the growing out process to minimize the demarkation line that will occur.

Good luck with your growing and color!

I know this is an old thread, but here's what I did.  When I decided to go gray, I had my hair frosted.  (I had been coloring for years, so it was my last hair coloring venture)  As the grays grew in, it looked very natural.  Now that my hair is down to my waist, I am really proud of my gray hair!