choosing hair color

I finally gave in and started coloring my hair--I started going gray in my early 20s & now 39, I can't stand the gray. I can't afford a colorist so its Loreal, and those aisles of boxes and boxes of happy hair colors. My haircolor is light brown with warm/gold tones naturally. All haircolors seem to turn my hair brassy. My current color is Loreal Medium Blonde, not bad really on my hair, but a little reddish.

My question is, should I use a 'cool' tone, an ash blonde? Will it tone down the reddish thing my hair has or just clash badly with my skin tone??

Does anyone know? I want to find a color and stick with it!

Thanks if anyone has any advice.

--Sara