I'd say special effects Green is the best, but lavender and green based dyes are the hardest to take so make sure your hair is as light as possible before dyeing and always try a strand test before use. You can see some dye result photos and dye help on the following links:
Gallery:
http://www.beeunique.co.uk/greenpage1.ht...
Hair Help:
http://www.beeunique.co.uk/hair-main.htm...