If you dye dark brown over your current hair colour, you’ll have to wait for it to grow out before you can do any crazy colours. Try a semi permanent like L’Oréal Castings in dark brown. It washes out in about 28 washes I think.
I’ve been bright pink a few months ago, blue, currently I’m purple (or as my 2yo nephew says: puppa hair) The Schwarzkopf Live colours wash out in 5 or so washes. The pink is definitely the most long lasting, the purple is more violet & turns pink after a few washes. The purple in my hair atm is BRITE from Woolies for <$10. It’s very vivid, but it made my bathroom look like two giant squid fought to the death in there. It washes out in 5-30 washes, which is a bit vague. My brown top hair has a slight purplish tinge left, my balayaged ends & bleached side streaks are still bright purple & I’ve washed about 7 times.