I'm not sure what brown flour is - at least where I live in the US that is not something I've ever even heard of before.
I know that our whole wheat flour is sometimes bleached. This doesn't change the color (much?), but it kills a number of nasties and thus makes raw flour safer. (you should still never eat raw flour, but if you do bleached is safer... I know many people do eat raw flour, but there are some things can can hurt/kill you if it isn't cooked). I'm not sure if whole wheat is what you mean by brown flour or not.
I know that our whole wheat flour is sometimes bleached. This doesn't change the color (much?), but it kills a number of nasties and thus makes raw flour safer. (you should still never eat raw flour, but if you do bleached is safer... I know many people do eat raw flour, but there are some things can can hurt/kill you if it isn't cooked). I'm not sure if whole wheat is what you mean by brown flour or not.