The hair always looks the wrong colour and that there is way too much of it, straight out of the box.
I'm always amazed that by rinsing & brushing it through, playing about with it and ultimately attaching it, that it infact matches & blends with my own hair very well.
Its hard to truly judge the colour until its cut-in.
Likewise density.
Once a few inches have been chopped off it stops looking like such a mass of hair.

It happens every time.
I recommend you work with it and judge when its cut & attached.
Also, applying a bit of grooming product to the back & sides of your natural hair will darken it a shade or two with no need to dye it.