this is VERY common in formula fed babies. im sorry about your breastfeeding issues. :( that sucks.
i want to stick in an encouragement, if its not too late, to just keep nursing along with the formula, that will help a lot.
otherwise, you can give your baby a little bottle or sippy cup of water. its likely that he wont take water in the bottle.
www.askdrsears.com
dr sears recommends the water for formula fed babies since formula is more concentrated than breastmilk, it plugs babies up.
you might hear its dangerous to give babies water, and yes, when given TOO MUCH water, it could be dangerous. however, its unlikely that baby will drink too much, unless you give it when baby is extremely hungry.. which is still unlikely cuz baby wont want the water then...
anyway, there are articles out there that say NO water for babies, but they are just saying that because its hard to say per baby and for babies age weight size, etc, how much to give. i would say add a couple ounces at a time and see how baby reacts. water is VERY important to formula fed babies.
the change in color is normal, its due to the foreign stuff. lol.
also, if your baby is eating some baby foods, its ok to get a box of milled flax and add it to the food. it works like a charm. stool should NEVER be hard, not even in adults, that means you arent getting enough fiber and water. fiber absorbs water in the stomach, and passes into the intestines undigested, but full of moisture. when a person and a baby has enough fiber, stool will always be soft and easy to pass. not watery, just soft. and it isnt a bad thing to have to give the flax every day, and it isnt a bad thing to add it to your own foods! :D its good stuff, that fiber!
anyway good luck!