Complex View Involving Separate Entities / Taxonomy Vocabulary / Content - Distinct
You can cheat a little and use Views Limit Grouping to help do this.

I created a view of smart phones with the path being smart-phones/%/colors. The only argument I need is for the OS. Add a contextual filter for the mobile OS using "Content: Has taxonomy term ID", filter by the term name. Under your fields to be shown, just select the color.

Using the Group Field (with Limit) formatter, we'll group by the color and show 0 items. Now if there are smart phones that have a color selected, it should show up in this list. In my screenshot you can see that I am only showing Blue and Orange, but in my taxonomy I actually have Blue, Green, Orange, and Red available - but I have no phones that are Red or Green.

From here, all you need to do is rewrite the color url to go to whatever other view you would like, such as smart-phones/%OS/%Color