Customer is using Solid Edge with a dark grey background and when creating 3D Sketch elements, those elements are created with a light grey color; the contrast of the light grey elements on the dark grey background makes it difficult to see the elements i.e.
Under View > Style > Color Manager the user has set the default color for their construction geometry to be using a style called Konstruktionen:
This then causes the 3D sketch elements to be a light grey color:
If you go to View > Style > Styles and under Face Styles select the Konstruktionen style and Modify it:
Under the Edges tab note that the color is currently set to a light grey:
Change this color to some other color e.g. red and Apply the changes:
Now the color of the 3D sketch elements has changed to match our selected red color: