Shape and lines magically changed color on class diagram?

[Adam Smith]

Some of my classes and their connectors turned red by themselves. How
do I change them back? I've tried everything from fill, to line, to
format, everything with no success.

Thanks in advance.

Adam Smith

 

[RA]

The red line means that there is an error.
To get rid of it, highlight the shape, format line and set the line color to
black or any other color.

If it doesnt work, click on Window\Show Shapesheet.
Find the LineColor cell in the Line Format section and remove the "Guard"
clause.