The only way to customise any colours on a Nuage display was to use Cubase rather than Nuendo. If you used Cubase the meters were blue, Nuendo were orange. With the latest update to the meter colours this is no longer the case so no, there’s no way to change any of the preset colours.
The Nuage software does get sporadic updates (mainly for compatibility these days). Functionality-wise there’s not an awful lot they can do to improve it. I’ve found a few bugs in the software (nothing show stopping) but hardware-wise it’s pretty much as near a perfect a DAW controller as you can get.
If I were using just a fader unit I’d set that up in the centre of my workstation and have the project monitor off to the side at a 45* angle.
As Fredo says, the master unit is a great addition (at a not inconsiderable cost) but I can see the benefit of using just a fader unit on it’s own but there are other 3rd party fader units which will do 60-70% of what the Nuage fader unit can for much less cost.
If the budget can stretch I’d say get the master unit as well as the two together are practically unbeatable as a DAW control system but the fader on it’s own will still increase your workflow ease and speed.