Multiple axis plot (bar:y, line:y2) draws the bar graph with 0.5 opacity

[smartDev]

I am attempting to draw a bar plot and a line plot on the same plot with separate axis.
I have achieved this, however the bar plot is always partly opaque, instead of completely opaque.

I’m not sure what to do to change this, it seems to be a default setting in plotly, as every attempt I’ve made to change this has no effect.

[etienne]

Can you share a reproducible code snippet? Thanks.