Grey hair -- to colour or not to colour, my child asks the question

I have grey hair. In fact, I have many grey hairs. I also have many more dark brown ones, so overall my hair doesn't look very grey. But they're there, and they are quite visible.

As my son pointed out last night. We were sitting around the dinner table and he leans toward me, points towards the part in my hair at the scalp, and says "Gee mommy, you have a bunch of grey hair. Why don't you dye it?"

Good question, but still, who wants their grey hair pointed out?

I have dyed my hair before. Three times, to be exact, unless you count that time in high school when my sister and I did home highlights that turned the tips of my hair kind of burgandy in colour). I am not one to colour her hair. I've always liked my dark, full brown head of hair, and have always been one for the natural look. But last year when I turned 39, my hairdresser talked me into doing a colour. So I dyed out all the grey, and while I got a few compliments, mostly no one noticed. And no one said anything when the colour faded and the grey grew back in. I dyed it two more times this past year -- well, I turned 40 after all!! But they dye is growing out and the grey is growing in, and now someone has noticed.

Should I keep dying my hair to hide the grey? I guess I look younger without the grey, but I know I don't look 40, so does it matter? Should I stay a staunch advocate of the natural look, or use what humanity invented and hide the ravages of age?

Should I let my seven year old decide this for me?