Can I dye my auburn hair ash brown?
I'm afraid you'd have to pre-lighten it first. Which can sometimes be tricky, as i've often seen hair go platinum blonde at the roots into a bright auburn-ginger at the tips. But this has been on hair that has been dyed brown many-a-time. If I were you, I'd buy a box of pre-lightener. A good one, not a cheap one. A box of ash brown dye and a box of darkest brown dye.
If it goes wrong, dye it with the ash brown, as a base, then dye it with the darkest brown.
Hope this helped.