Colour matching woes

I’ve been making trousers in a very special wool fabric. The colour is difficult to describe; the best I can do is “warm grey”. There are both brown and grey threads in the weave but from a distance it looks like a solid colour. Finding matching notions for fabric isn’t always possible but I wasn’t expecting this one to be so difficult to match. In the picture above are four YKK trouser zips in coloursĀ  (left to right) named “stone”, “light grey”, “dark grey”, and “charcoal grey”. They’re sitting on top of my fabric. I took the photo in natural light. Stone is far too light. Light grey looks green, dark grey looks blue, and charcoal grey is too dark. Those are all the greys available, and the YKK brown shades are all far too brown. I’m going with the charcoal grey (far right) on the “always go darker” principle. No doubt I’ll find uses for the other three.