Hi........recently I decided I wanted my hair lighter......I had dark brown hair.  So I highlighted it at home and it turned way too light.  Freaky blonde with dark brown, so then I dyed it back, which of course lightened rather quickly.  So I put sun in on it to get the roots to blend in.  Now it's pretty light and I sorta like the color.  The thing is I figure in the winter I would like my natural color back, and someone told me I can't dye back over sun-in that it causes major damage, I've heard about melting and hair falling out.  Please someone how can I fix my hair wihtout having terrible roots.....is there a time frame i need to wait or something I can do....PLEASE HELP...

Oh my!  You have quite the predicament.  I know that Sun In is one of the most harsh methods of lightening your hair.  That combined with the other chemical processes, I'd be afraid to do anything more to your hair.  Maybe consulting with a hair stylist that specializes in coloring would be the next step.  They might be able to recommend a course of action that won't destroy your hair.

Good luck.

I know that my hair is damaged.....I have been conditioning it a lot and it is actually in pretty good shape.  I just heard that sun-in has some chemical in it that reacts with hair color that causes it to melt and/or break off.  I am not sure if it is true, it is just what a friend told me.  

Sun In's ingredients:  Water, Hydrogen Peroxide, Hydroxyethyl Cetyldimonium Phosphate, Ppg-10 Butanediol, Quaternium-80, Panthenol, Silk Amino Acids, Polysorbate 20, Fragrance, Benzoic Acid, Disoidium Edta.

It comes with this warning:  Sun-in is not recommended for color-treated hair.  It's preferable to wait one week after permining your hair before using Sun-in.  Using on darker than recommended hair types may produce reddish tones.  Avoid contact with skin, eyes and clothing.  If skin irritation or redness occurs, discontinue use.

With these kinds of warnings and ingredients, I'd be very careful about additional chemical processing.  I don't know about the hair "melting", but I'm sure it is damaged and would be easily broken off if additional processingn occurs.

Do you like how it looks right now, and just want to fix it later?
The biggest reason you aren't supposed use sun in with color is because it is essenialy bleach, and pulls the pigment out. But when you have color added the pigment is not quite like natural pigments. You can pull the easier to lighten parts of the pigment but not others, leaving you with orangey or greenish tones (that's also why you wouldn't want to use it on dark hair). Dyeing over it is hard for the same reason. It's also harsh on the hair of course and if it is already damaged now it might be a bit much to dye over it.
Can you wait some and then later get a trim and have a professional fix the color? Doing it at home can be more damaging if you have to go over it to fix it or if you use something harsh. Aveda color has the lowest ammonia of any of the salon colors. That might be easier on your hair and the colors are really nice and natural looking.
You could also try using something like Loving Care, or a color depositing shampoo if you think that can give you the change you need.