You got me to looking up mole photos and I see that there are various species with differing fur colours, some North American species having a lighter coat than your British moles.

Darker or lighter, the colour does tend to be more or less halfway between brown and grey.

In ordinary US usage "taupe" generally refers to this midway colour, a colour which here in the US can't properly be called either "brown" or "grey".

An interesting thing is the way that different languages and dialects often draw the line between colour-names in different places along the spectrum.

I have seen, many times, UK clothing sellers using the word "brown" to describe tweed which generally in the US would be considered halfway between brown and grey. Americans would call the same tweed "taupe" (if familiar with that word) or "gray" or perhaps "brownish gray" or "gray-brown". More artistic types might call the same tweed a "warm gray".