Hi Mrs. Ali,
Thank you for your query.
I would have been in a better position to comment on the skin that you are mentioning if I had seen a photograph of your daughter. However, the description provided by you suggests that your daughter probably has naevus which are dark in colour. These are congenital and nothing needs to be done for it.
Regarding the colour of the face changing to blue and black needs to be examined by a doctor. A blue colour suggests that the child may be developing cyanosis
. If this is correct then a proper cardiovascular evaluation is required.
I hope I have answered your query to your satisfaction.