Let’s say – hypothetically – I dyed my hair and it came out much lighter in color than I had hoped. How long must I wait before dying it again (in a darker color)? Days? Weeks?
My wife tried to dye her hair blonde a while back, but it came out somewhat orange and she hated it. (I thought it was pretty cool, but she didn’t like it.) She dyed it back to her normal brown the very next morning, less than 12 hours later, and her hair is fine.
ETA: Both times she just used regular purchased-from-Kmart Garnier or Loreal hair dye. The stylist she called told her to use the Medium Brown coloring because it had nothing in it that would play off the other dye and make it look weird. And sure enough, it looked perfectly normal when she was done.
Ah, this is just what I wanted to hear. 
No bleach would be involved – I’d be staying in the brown spectrum – and my hair is healthy. I just wanted to know what my options were in case things went horribly awry.
Thanks!
If at first you don’t succeed, go to a professional stylist for the re-do.
Hair is dead so when you dye it it always is effected. Waiting longer isn’t gonna help it. If you continually dye it, you have to wait till it grows out otherwise you get mixed results. A long strand of hair that is overworked from too much dye and part of it OK with the dye and the new part growing in that is uneffected.
I used to dye my hair a lot so I know. Orange is typical of dark haired people. No matter what boxes say you cannot go from any kind of brunette to blonde. You need to first REMOVE the color and bleach all the color out. You wait a day then RE-DYE it the color blonde you want.
You can use various things like conditioners but eventually the hair suffers from too much dying, even without bleach which is hard on hair. Celebrities often will wear wigs while they let their hair grow out.