I managed to find a very ugly workaround to deal with this.
It seems that the figure starts with 3 colorscales. And, as soon as I trigger any hover/highlight event, 2 more colorscales are created, for a total of 5.
The default (viridis) colorscale seems to be always the 3rd one. Thus, I added a little JS snippet that hides its layer on window load:
```{js}
function code_default() {
document.getElementsByClassName('infolayer')[0].getElementsByClassName('colorbar')[2].style.display = 'none'
}
window.onload = code_default;
```
Does anyone know of a better way to deal with this?