All the Assembly files have to have the same CDF (Color Definition File). When you add a component to an Assembly, the color of the Component, as seen in THAT Assembly, will be based on whatever color was assigned to the color ID assigned to the solid body of the component in it original master file.
So, let's assume that you're running a recent version of NX (say NX 6.0) and you're using the out-of-the-box assigned colors and you create a Part file and assign it the Color 'Blue' (Color ID=211). You now add this Part file, as a Component, to an Assembly file which is using the same out-of-the-box colors and it that case the Component will appear to be
Blue in color. However, if you were to add this same Part file to an Assembly file where someone had edited the color palette (or perhaps it's an Assembly file created in an older version of NX/UG using what would now be considered an out-of-date color palette) your Component part, in THIS assembly, will appear in the Color that has been assigned to Color ID=211, which might now be Red. In that case your Component will appear to be
Red, but ONLY in this Assembly file.
Now you have two choices if you wish to have consistency across all assemblies, either edit the color of the Component file (in the context of the Assembly) to match your desired color or decide on a standard and make sure that all Assembly files are using the same Color Palette.
Note to change the Color Palette of an existing file you will need to go the Preference menu to do that. Prior to NX 6.0, you would find this under...
Preferences -> Visualization... -> Color Palette (tab)
...where you find at the top of the dialog a section where you can assign/change the CDF file.
Starting with NX 6.0, there is now a dedicated Color Palette dialog on the Preferences pull-down menu where you will find the CDF options at the bottom of the dialog.
Anyway, I hope that helps explain what's probably happening.
John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Cypress, CA
To an Engineer, the glass is twice as big as it needs to be.