you seem to be allergic to the hair color.. and i also feel you have symptoms of Seborrheic dermatitis
what i would suggest is you avoid the hair color your using. there are many specially formulated cosmetic products specially formulated for people who are allergic to commonly used cosmetic. you will to find out the brands which sell those in you city.
and the steroid
which your using orally has lot of side effects if you use very often. i suggest you use it only when it is really required. and please consult another dermatologist
and take second opinion
regarding your dry scalp
and itching it could be Seborrheic dermatitis which needs proper treatment.