Splat His and Her Rebellious Hair Color. Question for hard core hair dyers.?

I have dark brown hair. I love it, but Im ready for a something a little more fun. Ive been looking into Splat His and Her Rebellious Hair Color in Lusty Lavender. From what ive read I would have to bleach my hair (which i refuse to do) before I dye it. So, does anyone know how it might turn out if i don't bleach my hair first and put the dye on my very dark brown hair?? I want the end result to be a very dark rich purple. Is there anything extra I can do to get the results i want? Thank you in advance. :D