Breastmilk typically has a bluish, watery appearance once the copious amount of milk has "come in." Colostrum, or the first milk, is yellow due to a large amount of beta carotene.
Breastmilk sometimes looks pink or like strawberry milk. This may be due to damaged and bleeding nipples. This milk is usually fine for your baby.
Rusty colored milk, known as "rusty pipe syndrome," is probably due to old blood in the ducts themselves. Though alarming for a mother to see it is fine for your baby to drink.
Breastmilk also sometimes has a greenish appearance, which is also fine for your baby to drink.