Adage says the secret to creating the most flawless face, is to wear makeup but create the illusion that you aren't. An appealing process; but honestly, it's not always ideal. Sometimes we crave the red lips, right? And cherry smackers truly aren't all that natural (although if it is for you, do us a favor and just pretend it isn't).
Ombre hair color is the same in my book. There's a beautiful subtlety to cascading hair that gives an illusion of color differentiation (see beautiful model 5) but then there's also a tinge of excitement in the drastic chocolate to white-sand stunner (like 3).
The main concept to not stray away from no matter what your fancy is: start with a small area of change.
Work with an experienced hairdresser whom you trust and throw around some ideas with him or her. Look at color samples that work best with your own current or natural hair and build off of that. Think of it like painting the walls of your house. Pick a color that amplifies the undertones of that vintage restored hardwood floor to a mesmerizing audience.
And if you aren't pleased with your choice, try again! Once I painted my bedroom three different colors in one weekend. I don't encourage such labor, but I was so pleased with the end result. I had the color I dreamed of and didn't mind working a bit to get there.
So, after making the initial plunge and calling for the appointment- make sure you assert yourself and pick the color that complements YOU! There is no standard ombre, just like there is no standard you. Embrace your uniqueness, and go ombre!