I'm not sure at the moment whether this is by design, but doing HCL interpolation with gray values seems to behave strangely: <a href="https://elm-visualization.netlify.app/colorspaceinterpolations/iframe.html?start-color=%2300ff00&end-color=%23919191&number-of-colors=28"><img width="1025" alt="Screenshot 2023-09-20 at 13 36 22" src="https://github.com/gampleman/elm-visualization/assets/69144/f97daa07-458d-43fb-9f84-0c8e8d69944e"></a>