You can find the color flags above each preview in the edit mode of your galleries. You also find them below each preview in the large single file view.
Color flags can support the different stages of your editing or selection process. Just like you are used to in other programs.
For example, you can use the color "green" to mark files that you feel are ready. Your client can set them to "final" if they feel the same way. Or they mark files as "orange" again if they still want some changes. Of course, this is only one example of many ways you can use the color flags.
It is possible to give the color flags their own names. You can also hide individual color flags if you and your customers don't need them.
With these flexible settings you can set up your workflow exactly the way it suits you and your customers.