Ion Color Brilliance Brights, probably the best unnatural dye I’ve used. The colour stays in, and I mean it stays in.
I’ve coloured my hair with the Aqua and the Teal. It’s been three-ish months and I haven’t had to re-dye the Teal (I dyed over the Aqua with the Teal). It’s also, very affordable, 4.99$ I believe. There’s no Ammonia or Peroxide and it’s ready to use. And since it doesn’t have those chemicals it doesn’t make your hair feel like crap. Unlike Splat it doesn’t stain you for weeks, scalp included.
If you’re looking for good unnatural hair dyes, I recommend this.