default color scheme for plotly contour plot lines

[pyroman1337]

when several plots are combined as subplot, plotly R contour plots use different colors for the contour lines (since an update some months ago). Sadly, after 5 different colors there seem to be no more available and the subplot cannot be created. How can the contour line colors be set to be the same for different subplots?
My example shows this issue when the "grouping variable" is set to "block": https://sae-interactive-data.ethz.ch/sae-eschikon-live/