Can I put a semi-permanent dye on top of another semi-permanent dye?

I have had an absolute hair disaster just this week...

I was originally a bleached platinum blonde. This past weekend (Saturday), I had a horrible experience with my usual boxed blonde color.. the color inside was either wrong by the company or switched by someone as a horrible joke and my "blonde" turned out a light brown with an ash-ish tint on the tips. To fix this problem, I put on a permanent Loreal color that was a rich auburn brown. This was a perfect solution for about 2 days. After 2 days however, my light tone of blonde-ish brown is starting to show through on the tips. Tonight, I tried putting an auburn semi-permanent that was ammonia free on my hair to coat the tips more thoroughly and now my tips are bright red.. YIKES! Basically, my question is...

considering that the semi-permanent dyes are ammonia free and contain natural ingredients (this is natural instincts brand), could I go up and buy a new semi-permanent darker shade of just plain brown (like a chocolate) and put it on my hair tomorrow? I have work and the shade of redish pink that my hair is now is just not acceptable.

PLEASE help!