How does one control the color of sketches shown in a part file?
When editing a sketch in a part file, the colors are defined in the Solid Edge Options> Colors tab, this is well known, but when you are not editing a sketch, the color the sketch shows while displayed is controlled by the Construction Default face style.
To modify the color (do this in your part template file if you want your new parts to reflect the new color. This will also change the edge color of all construction elements such as surfaces and bodies in the file):
In a part file, go the View tab and select the Styles command
Set the Style Type to Faces Styles
On the Styles list, select Construction Default and click Modify
Select the Edges tab and modify the RGB values and the H(hue), S(Saturation) and I(Intensity) to change the color. A preview is shown on the top left so you can have an idea of the changes you are making.
Once you find what you want, just click OK and Apply. All sketches and edges of construction elements s in the file change to the new color.