OK, I think what you're seeing, it all took place in NX 6.0 but it's possible, as you're already mentioned, that you've somehow missed it.
To start with, it is true that we changed the 'Color Palette' in NX 6.0 from what it was before that, which was the original 216 color scheme that was introduced in Unigraphics V17.0, but which was not changed to be the system default until NX 3.0. I know this old color palette like it was my own, because in many respects IT WAS.
I was the product manager for this effort 10 years ago when we released V17.0 and upped the number of colors from the previous 15 (16 if you counted the background) to 216 colors. As for the names and the RGB values of the colors we chose to include in the new palette we depended on some work which had been done by an organization named 'VisiBone' who at the time had just published a guideline for use of colors when designing webpages. While this was not directly related to our work, it was the closet that we could find without going out and hiring a so-called 'color expert'. For more information about this 'VisiBone', go to:http://www.visibone.com/
Anyway, from this we adopted what they referred to as the 216 color-cube (just look at the color-palette dialog in any version from UG V17.0 thru NX 5.0 to see what I mean by a 'color-cube'). The cube (at least I thought so) was pretty self-explanatory and it did do a good job of showing how one would distribute 216 colors in an even and logical manner from White to Black. The problem was that it was a little TOO perfect. That is, it provided a mathematically perfect distribution in terms of the differences in the RGB values from one color to the next across the 216 color slots. Unfortunately the human eye does not actually work quite that symmetrical when it comes to perceiving the differences from one shade of color to the next. For example, one of the complaints was that there were too many Blues and Greens and not enough Grays and Browns.
So for NX 6.0 we decided that as part of the effort to future implement the new style dialogs introduced in NX 5.0, that when it came to the 'color-cube', we needed do something drastic and it was also about this time that someone decided that perhaps we really should hire a 'color-expert' (actually it was a software user-interface expert whom we had already 'hired' to help us with the NX 5.0 project to update our look, feel and behavior of dialogs and who had also commented that we really needed to do something about out choice of colors). So based on the research that was done and looking at the complaints that we had been getting over the years as well as what a new color palette dialog might look like, we decided to make a make a shift in colors and abandon the 'perfection' offered by the 'cube' and pick a set of colors more consistent with the way people actually looked at and perceived colors.
Now we do one thing, when looked at the new color scheme we assigned the numbering such a way that if you had been using NX since at least NX 3.0 and had been running based on the out-of-the-box defaults, that when you started to use NX 6.0 and you created a new part file you probably would hardly notice any differences. Of course, if you had been using a large number of different colors then things might appear like the changes were more drastic and besides, any legacy part files were not going to have their old colors replaced with new ones anyway since the color palette has always been and remains, part specific. Of course if you mix old parts with new and particularly if you added old parts to a new assembly, things could start to look very different (not as bad as when we went from NX 2.0 to NX 3.0, but still noticeable). Now we have not made any other changes to the color palette since then.
OK, as for can I go back to the old colors, while we would like to encourage people NOT to, we realize that that may not always be practical so we have included a copy of old pre-NX 6.0 color palette, whcih can still be used is desired, with each release of NX since NX 6.0. Just go to the UGII folder of your install and look for a file named 'ugcolor_nx5.cdf' (the default color file is 'ugcolor.cdf'). You can use this file to replace the color table in any existing part by using the options at the bottom of the Color Palette dialog and you can go to...Customer Defaults -> Gateway -> Visualization -> Color Palette
...change it there so that the system will now behave, with respect to the colors being used, as it dd prior to NX 6.0 (but I must warn you that with the 'color-cube' the old colors will not look as logical when viewing them using the new color palette dialog layout).
OK, I hope that clears up the color issue.
But you also mentioned that 'curves' and other objects are different. Well this might be the result of ANOTHER enhancement we made in NX 6.0 and was something called 'Wireframe Contrast'. One of the problems is that when looking a shaded solid, the color selected will give you one impression but if you were to that some color used for a wireframe display it would look totally different. Colors that look good when seen as shaded model sometimes look washed out or hard to see when you turn shading off and all you see are wireframe edges, even if the background color stays the same. So for NX 6.0 we add a scheme, referred to as 'Wireframe Contrast', which changes the color of any wireframe object, irrespective of what it is or whether other objects are being shown as shaded or not, so that it will have a higher contrast with the background. Now this will actually cause the color of wireframe objects to change color depending on whether the back ground is light or dark AS COMPARED to the color of the wireframe object. This means that lite-colored wireframe object will appear darker on a lite-background while darker object might not look any different than what you would expect. And of course the opposite would happen with a dark background.
So to see how this works, either turn off shading or open a model with lots of curves and go to...Preferences -> Visualization -> Line
...and in the section labeled 'Session Settings' try toggling ON and OFF the 'Wireframe Contrast' option (hiting the 'Apply' between toggles) and nothing the change in the display of the wireframe objects (note that there is no Customer Default for this, only the preference which will be remembered by the registry).
Anyway, sorry for the long reply, but I thought you should know the whole story. BTW, we did discuss both the color changes (at least somewhat) as well as the Wireframe Contrast option in the NX 6.0 'What's New' document under...NX Essentials -> Preferences
...so check it out.
John R. Baker, P.E.
Product Design Solutions
Siemens PLM Software Inc.
To an Engineer, the glass is twice as big as it needs to be.