Praise be to Allah.
Istikhaarah is mustahabb and is prescribed in Islam, but one does not necessarily see a dream after it or get an answer as you described. Rather its effects appear in the matter being made easy. If the matter is made easy and goes ahead, this is an indication that it is good, in sha Allah.
The son is not obliged to obey his parents with regard to marrying a particular woman, but if he does that to please his parents and make them happy, he will be rewarded for that, so long as the woman is religiously committed and of good character.
If he gives the matter some thought and decides that the woman is not appropriate for him, and is afraid that he will develop resentment towards her or that he will later be forced to divorce her, then it is better for him to tell his parents frankly about what he feels and to apologise to them for cancelling his engagement. This is better than going ahead with something he does not really want.
We advise you to think long and hard and to examine your fiancée’s characteristics, both positive and negative, before taking the decision to cancel the engagement. If she is religiously committed and of good character, and has no faults other than what you mention about her hair, then this can be dealt with. And a woman may be beautiful or acceptable despite that problem.
But we also think that you should delay going ahead with the marriage until you have put your mind at rest about that decision.
You should offer a lot of du‘aa’ (supplication) and ask Allah to guide you to that which is best in this world and in the Hereafter.
See also the answer to question no. 26852
And Allah knows best.