""Blue" is a broad term that I think most people will consider contains everything from turquoise to indigo"

It's been a long while since I've read Berlin & Kay; but, as I recall they asked native speakers to segment a colour array using their language's basic colour terms. Thus a broad range of hues identifiable with that term could be identified. Subjects were also asked to point out the foci for each basic colour. Berlin and Kay found that, cross-linguistically, the foci for colours like red, yellow, green, etc. were fairly consistent, though the range of colours so identified varied enormously. Essentially, the more colour terms your language has, the more tightly you draw the boundaries; but you'll always put the central colour (e.g. the ideal red, the perfect example of blue, etc.) in much the same place.

My recollection is that, when plotting English colour terms, they wound up with a a big gap where true turquoise shades would be. Then again, they didn't consider "turquoise" a basic colour term; so their subjects would not have been allowed to identify colour chips as turquoise.

Without having the book in front of me, I can't tell you what their test subjects picked as focal blue. And, as I recall, they told readers up front that the printing process made the picture of the colour array inaccurate anyway; so that doesn't help much!

When we do the next colour, I'll be sure to do my best to show focal blue and turquoise for me. But it'll be by what I see on my monitor; so there's no saying how you'll see it.   :(