"Sienna" is an extremely ambiguous color already. Image search for "sienna color" and you'll get a huge range of browns, reds and oranges.

"Burn sienna" seems even more varied. Here's are four different color-oriented websites, with a dark earthy orange from Colorlex [1], a light salmon from Canva [2], a light brown from Benjamin Moore [3] and a dark brown from Atelieracrylic [4].

1. https://colourlex.com/project/burnt-sienna/ 2. https://www.canva.com/colors/color-meanings/burnt-sienna/ 3. https://www.benjaminmoore.com/en-us/color-overview/find-your... 4. http://atelieracrylic.com/atelier-interactive/burnt-sienna/