Great advice, folks!
Chris - how did you know I had color perception issues? Is it obvious from my painting...?
I seem t recall we had a similar discussion some years ago - I don't know the specifics anymore, but I think you mentioned it would be helpful to use specific colour references (e.g. for Vallejo codes).
I agree that for dusting and weathering, especially in a very dry and dusty climate, chalky tones are the way to go. I would suggest though to use lighter shades to actually highlight a colour area and use the chalky, dusty stuff only sparingly for highlighting and weathering. I'll put up some other pics of 'dusted' vehicles later on.
I'm sorry if it comes across as patronizing, which is not my intention, mind.