Difference in pigmentation is common in childhood, make sure the baby is fed adequately. This should mostly reduce by itself in a few weeks.
Next Steps
for daily shampoo rather than washing the whole head, use a cotton bud and wash specific areas.
Health Tips
evaluate the hypo pigmentation for any
vitamin deficiencies after 2 to 3 weeks if you are worried.
keep the skin moisturized (try and avoid oil). you can use good baby moisturizers.