Technically the color is applied on the hair and very little touches the scalp. From this again very very small quantity may permeate the skin. The color getting to the baby thru breast milk and affecting the baby is not possible. Just don't color hair around the baby. Once washed off the chemicals are removed.

Thanks Sheetal

my doctor advised me not to at least till the baby is 6 months old. and I went to Lakme and they suggested the same.