tips for dying hair green?

spaghetti

can't speak for brands because i'm not in the global north so i don't know what brands you have available, but i can give you a few tips that helped me:

• bleach opens your hair's porosity, this is how it retains the color once dyed. after dyeing it you need to restore your hair's porosity to keep it from fading. some professional moisturizing creams can help. likewise if your hair is not porous enough at first after bleaching, it won't take dye as well
  
• due to the composition (which goes into chemistry that goes over my head) blue-based dyes (such as green and purple) can last shorter than red-based dyes (such as pink)
• try to always wash your dyed hair with cold water to keep it from fading. additionally, make sure your hair products don't contain salts or alcohols, those also cause your dye to fade quicker