Wonder about the color of this soup

They also might have used Yukon gold potatoes, even though the recipe calls for russets.

The powdered cayenne and paprika peppers will absolutely affect the color.

As Nancy mentions we don't know if the food stylist took any liberties in the interest of artistic license.

Another factor is the vegetable stock. I make my own and I don't follow a recipe. It changes each time and some ingredients frequently make my vegetable stocks quite dark; carrot peels and yellow onion skins do this.

In fact, cooking yellow onion skins is a recognized technique for dyeing textiles:

https://www.folkfibers.com/blogs/news/6652230-natural-dyes-yellow-onion-skins

Remember that for most of human history, natural pigments have been derived from plant, animal and mineral sources, long before the advent of industrial pigment manufacture.

Paprika and cayenne will do it.
And we dont know when they were added for the photo, or what else the stylist may have done.