"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/

Worth watching the Technology Connection video on the colour Brown [1]. It's a strange colour that only really exists when placed in the context of other colours, not something that can really be produced by a pure RGB light source, which explains why the CSS Brown colour looks red.

[1]: https://www.youtube.com/watch?v=wh4aWZRtTwU

I tried to find brown on the slider to see what you’re talking about. Took me ages. Turns out you have to go REALLY red in order to find brown.