Changing Default Line Connector Color in Visio 2013: How To?

[HappyCamper]

HELP, please! 

I am difficulties with changing and keeping the change of the default connector line color in Visio 2013. 

I get that the color is defaulted in the Theme and using Style.  I don't think I'm doing it right. 

I can change the color of the connector line using by updating the theme and changing the theme colors of the connector line to black.  But then that I can't repeat that color change on future pages/stencils/files.  It seems that Visio just goes back to the system default color of blue for line connectors.  I feel like I should be able to change the connector LineColor in ShapeSheet, but I don't know what cell to change in ShapeSheet, and then don't know how to set that as a default for future templates/stencils/documents.

Is there a good overview of ShapeSheet cells and how to use, that is not written in code-speak?

When I update what I think is the correct data element (cell) in ShapeSheet, Visio only keeps the black connector line for that particular file. 

I have discovered that if I turn the Theme off and use only black and white Theme, I can get black connector lines - which is NOT what the users want.  They want other shapes to maintain their themed colors (e.g., Swimlanes, separators, process, decisions, etc.) which are blue in this particular theme.  Can I change only ONE ITEM's style and then create a new custom theme?

Can we create a custom theme color palette that is "locked" for future stencils?  How? 

The template that I am trying to mimic is the company's old template using Visio 2007.  The users want black connector lines, not blue connector lines. 

What am I missing?  Where should I be looking? 

Thanks in advance for all advice and assistance!

[Nikolay]

Maybe this will help:
How can I change the default properties of Visio's connector tool?