Full head of dye, whether its done in the hairdresser or at home from a box, is hard to achieve a "multi tonal" look. If you have pre-existing highlights, that can do it, but a second application and they get "lost". Basically, you can't easily. Lots of the boxes claim "multi faceted colour" etc etc but in reality any full head tint will get blocky after a while.
I do my hair at home and these days I use professional dye (Loreal Majirel) however I went to the hairdresser the other day for foil highlights to give my hair that expensive salon look. But if I maintain my "base colour", I still save a fortune, as I am going a bit grey, and can do my roots whenever I want, but let the hairdresser do the hard bit which is highlights. That's what involves skill an expertise and time.
In reality, if you want Jennifer Anniston's look, you will need highlights, and lots of them, as well as lowlights, every 6 weeks, and a blend of probably 3 salon strength colours. However, that general tone is achievable in a solid colour.