Hi Roy
Have you tried Constraints - Attributes and Properties - Set Harness Attribute/Property on Object.
However, unless you wanted to make a constraint for each Wire (I don't think you want that) you would need to assign by an Attribute or Property.
Below is unusual but you would be setting the Color "B" onto any Wire that begins with "WB-" in its name e.g. WB-1, WB-2, etc.
You need some criteria for the Constraint to run on. Here I used Name. But if you were assigning a Property e.g. COLORPROPERTY and set the Constraint to assign B for a COLORPROPERTY of B... well, then it might be faster to simply set the Color manually.
Let's hope someone comes up with a better method - or let me know if you find one.
Regards,
Pat
P.S. You might prefer the following - please take a look: