Mona, I always keep my core neutrals in mind when I am buying colours. And I only buy specific colours.
My main colour and neutral is blue.
Navy and ink (and denim) act as a neutral for me. But I also wear blues in almost all shades and tones as colours (and I often wear blue with blue or navy with black or grey).
I do vary the blues by season a bit. So in summer I wear cobalt and small amounts of pastel blue (which I don't wear in winter). And in winter I wear teals and more navy and ink.
My other colours are basically the berry family: cranberry, fuchsia, raspberry...and also plums and orchids. Occasionally I will wear a green, particularly in spring/ summer. But I can think of only two green pieces in my wardrobe -- one is a blue and green pattern, and the other is that "Pond" J. Crew sweater, which they describe as a blue. Sort of an aqua, I guess.
Add the rest of my neutrals -- taupe, grey (all cool shades), winter-white and optic white, and that's about it.
Except for black. Black is a colour for me, not a neutral.
BTW, I was fine at the border because I was being pretty honest. I paid some duties -- I might be returning some of what I brought back (and paid for) when I go with you -- and will get my money back in that case! All bras and undies and Pleione tops were duty free!