Customize Color Scale doesn’t display on iPad
Tapping the “customize color scale” within Settings on the iPad application dismisses the Settings panel and doesn’t show the panel for changing the colors
Right there is no way to customize the color scale on the App. You have to do it on the website www.windy.com, on desktop/laptop.
On iPad it is possible if you use your browser with www.windy.com
See screenshot of my iPad with color scale settings page