A family of Microsoft presentation graphics products that offer tools for creating presentations and adding graphic effects like multimedia objects and special effects with text.
The Smart Art color dropdown is only enabled when you are working with a Smart Art object. This is not how you create a new fill color for your presentation.
Instead, try this on the Themes tab: select or create a them and apply it to your presentation. Then choose Insert>Smart Art Graphic, create a smart art object and apply a theme color to the elements of the smart art by selecting the object to color, clicking on the Smart Art Format tab and selecting a color from the Fill dropdown.
If I have misunderstood, please reframe your question using the names of the menu commands used in PowerPoint. I can't find any Smart Art Color Edit command.