Highlighting Kit gone wrong! Help

What did you use? I can't be totally sure that you used a dye solvent. But assuming you did, the hair will not be exactly like the nautral color you started with. This is because the permanent hair color used comes with a developer that lifts your natural haircolor about 2 shades before depositing it's own artificial color into your hair. What you are left with after the color removal is the underlying pigment minus the artificial pigment and this is warmer and lighter than your natural hair color. For this reason, you need to apply a toner afterwards.

But if you bleach it, then the bleach actually removes more of you natural hair pigment than the color did in the first place. In fact, bleach removes natural hair color faster than it removes artificial hair color. This damages the hair much more than dye solvent color removal alone. It will make the hair much more porous as a result and you will still be left with an unnatural color, albeit a much lighter color that also needs a toner.

That's just not true. Are you speaking from experience? Perhaps you were using a different type of color remover or one that actually contained bleach which I don't consider a hair color remover. There is actually a lot of technology in hair color removal these days.

There are 3 types of hair color removers and the one I am referring to, Color Oops, is a dye solvent. It shrinks the hair color molecules so that they wash out of the cuticle. It is much less damaging than bleach and does not remove the natural hair color. See my post entitled "Hair Color Removers: 3 Main Types". This will also give you a list of other hair color removers that are dye solvents.

If it's too dark, why not use a color remover like Color Oops , (a sulfate based remover that only removes the artificial pigment?) Then color with the demipermanent in a neutral or warm shade lighter than you want (they tend to come out darker than they look on the box). Going to a professional for a color correction is a good idea too but they will probably charge quite a lot. Don't be surprised if it costs $300.

I would recolor with a demipermanent shade like Natural Instincts or L'oreal Casting Colorspa in one shade lighter than your all over color in a neutral or warm shade. This should blend the hair nicely. Then get the highlights done professionally if you still want them. Hairdressers spend hours upon hours practicing highlighting techniques which is why we pay them the big bucks.

Do you mean you dyed your whole head, highlighted, then you didn't get the highlights lifted as much as you wanted?  What color did you dye your whole head?  Or did you mean you just got highlights that were an okay color but too chunky? 

Remember that color won't lift color, so that might have been your problem if you didn't get the lift you wanted from the highlights (I'm not a pro and not familiar with that specific kit).  If they just came out too chunky, this would be how you put them on.  Doing less hair and hair that is not so close together would make it more strandy and less chunky.