Unnatural hair colors are sometimes hard to achieve and then maintain. Here's a helpful article on how to get your hair from any previous shades to a vibrant green.

Steps

1. 
   1
   Buy green hair dye. Green hair dye is one of the scarcest colors of dye, so you might have to order online or scout around.
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2. 
   2
   Bleach hair or use platinum blonde dye. Apply to whole head or desired area. Keep on for time listed on instructions, no longer. Bleach can be extremely damaging when left on for too long.
3. 
   3
   After bleaching is complete allow hair to dry naturally, do not use heat. Before adding color, use a repairing treatment. Coating your hair in mayonnaise is a great way to kelp hydrate it and restore natural oils. Deep conditioning treatments also work. Your hair will be very dry if you don't use a repairing treatment after the bleach.
4. 
   4
   Section off hair by clipping up the back, the front, and both sides. Dye each section one at a time, and thoroughly coat each section, you can never use too much dye. this hair dye will stay in for 6 months
5. 
   5
   Leave dye on for directed time. For an even more vibrant look, keep the dye on for an extra 10-15 minutes, but no longer than that.
6. 
   6
   Wash out hair dye with cold water, shampoo, and conditioner.
7. 
   7
   Finished!