Hair that has been subjected to excessive heat styling or chemical treatments can become over-processed. Strands that are over-processed appear very dry and are prone to breakage. Coloring hair of this type presents a challenge and is best left to a professional. Hair is very porous and will absorb color quickly, however the color generally fades very quickly—leaving you with a dull shade that isn't what you sought. There are some steps you can take to restore health to damaged hair so that color lasts as it should.
Visit your stylist for a routine trim. Over-processed hair is prone to split ends and breakage; ends in poor condition tend to fade faster than the rest of your hair. If hair is extremely damaged and you have lots of broken sections, a stylist may be able to re-shape your style to better incorporate the pieces.
Use a deep conditioning treatment two to three times a week after you shampoo. Leave the treatment on your hair for at least five minutes after applying it generously from roots to ends.
Use sulfate-free shampoo and conditioner designed for color-treated hair. Avoid shampooing every day and instead rinse hair with water, condition and re-rinse. This helps your dry strands retain moisture and aids in preventing color fade.
Avoid heat styling as much as possible. This includes blow drying, curling irons and straightening irons. These promote damage by drying out hair further. If you must heat style, use a thermal protecting spray.
Visit a stylist for help with color when you're ready. If you insist on coloring yourself at home, apply a pre-color treatment to help strands hold color. Choose an ammonia-free boxed dye and only apply it to roots and grown out areas if possible.
Continue to follow the above regimen to help your hair become less damaged and hold color longer.