Are the rashes itchy?
From what you say, it might be extensive Tinea Versicolor
Tinea versicolor- is a fungal infection
of the skin that presents with white spots
. patches, usually itchy, seen in areas of increased sweating. It can be seen in scalp but will not cause discoloration of hair.
If hair is discolored, spots are seen on the bony prominences of the joints, hands, face etc its likely to be vitiligo. Its an autoimmune disorder of the skin- where antibodies
are formed against our own melanocytes.
Treatment varies according to the diagnosis.
You might get a dermatology consultation.