If you are using STB plot styles, create a layer and assign the plot style "normal".
If you are using CTB you will have to change the pen setting. Create a layer and assign for example color 100.
In the plot dialog box in the top right hand corner, click on the button to edit the plot style.
In the plot style dialog on the "form view" tab select color 100 on the left hand side. On the right hand side, click on the drop down box for "color" and select the color you want it to plot. Save and exit, etc.