Brown bread flour is considered as more healthier and nutritious than the white bread flour as it is made by whole wheat flour which contains bran, endosperm and the germ. White bread flour is made by endosperm only and the fiber rich part of wheat like bran and germ are removed from it.
Brown bread flour contains fibers, vitamins and minerals like B1, B2, B3, B6 iron, zinc etc. It also contains proteins and carbohydrates whereas flour manufacturers add potassium bromide and chlorine dioxide gas in white flour which is used to bleach the flour. Both have different taste and texture due to the contents they have, white bread is softer and tastier than brown bread.
Sometimes milk and sugar is added in white bread to give it a sweeter taste. Since brown bread is more healthier, some bread manufacturing companies add caramel to make it brown and sell it as a brown bread.