Hi,
your observation is correct, I must admit. And that's for two reasons:
1. In Alias curves don't have a line color property
The actual color used to display a curve is taken from the Layer color the curve is contained in. (By default, any curve is put into the DefaultLayer which itself has no color assigned).
2. By now, there is no programmatic way to define the line color of a CATPart's curve
Actually, Alias team already plans to set Catia V5's outline color property to the color as implied by Alias' Layer color (see above) which would in most cases resolve what you are asking for.
Unfortunately, by now there is no way to achieve this - and the libraries we are relying on here are not owned by Autodesk. We are already in contact with the vendor of these software libraries and try to get this bit of functionality as an extension.
Sorry for not being able to share better news on that topic - by now.
Best regards
Thomas
Thomas Rausch
Software Development Manager