@manu33
You must make the settings change on windy.com and be logged in with your Windy account. It is not possible to do this change in the phone app.
In the left high corner menu (3 horizontal bars), select, « Paramètres » > « Modifier les couches de couleur »
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Then you see « Select overlay Vent [wind] »
At bottom click on [show gradient].
It opens a small window that you can enlarge.
Delete all codes in this window.
Then copy the code in my post about wind settings and paste it in this window.
Click on [import gradient].
And finally click on « Save »
The modification will be applied in your phone app too.
Bon courage !