Verified answer

Use a color filler. Cheaper than a real expert, go to a Sally or something. They'll have the filler and can make a color recommendation. I don't think you need a special color, just something that will cover the strand instead of going into it. Hence the filler.

depends what product you used to tone it down its usually peroxide that works for darker hair to go light perhaps the percentage of the peroxide was too high as a result has turned your hair green. i'm sure any hair colour out there should cover up the green but be prepared for your to break dying really damages your hair. Hope i've helped :)

Oh. Wow. I am so sorry. This happened to my cousin once. She got her hair stripped of color and dyed it back to the natural shade. If you hate the natural shade or can't find it, just choose the color you wanted to dye it in teh first place, but a different (better) brand. Hope this helps!

either dye it over with a darker color OR wait a little then lighten it again to reach the blonde you want..