It could turn your hair blonde. Stay away from any color, that has ash in it. This color will turn it red. The lighter blonde you go, the better it will look. The darker your hair color is, the lighter blonde you need to use.
If u go to many shades from ur natural shade of brown to blonde without stripping it first it will turn an ashy green color. I suggest u go gradual to blonde. Start w a dark blonde n work ur way up. Otherwise go to a professional.
It will not turn orange and it will not turn green unless you do something freakishly wrong or already have those colors in your hair. Depending on how dark it is, it may take a few tries for it to turn blonde. I do agree though, that you should go to a professional and start with highlights and gradually add more. Otherwise your hair will be so fried.