People who have used henna hair dye before?

I want to buy this henna dye – http://cgi.ebay.co.uk/HENNA-HAIR-COLOUR-DYE-AUBURN-RED-see-our-models-pic_W0QQitemZ310129551820QQcmdZViewItemQQptZUK_Health_Beauty_Hair_Care_Hair_Colouring_Dyes_PP?hash=item310129551820&_trksid=p3286.c0.m14&_trkparms=72%3A1688%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318 I have very dark brown hair and i’ve read that it will highlight my only a bit, is this true? I don’t want to buy it and for there to be no change. Thanks