When using Plot->Add Curve(s)… to add an extra curve and changing the plot type settings, the extra curve gets the same color as the first. How can this be fixed?

This happens only if  is selected in Plot->Auto-Refresh.... To avoid this, instead of ‘all curves’ select ‘active curve’ as shown below.

Alternatively go to Plot->Layout->Edit… from where the curve colors can be set by clicking on the colored line shown below.