High definition Geological maps: where on Google Earth #223 revisited

I was very interested to discover that the British Geological Survey has made its superb maps publically available at the 1:50k scale. I know much less than I ought about the technicalities of all this, but I have found a link here which shows the data in Google Earth. I've edited it a little but it basically works out of the box. Obviously it only shows data from Britain...

One obvious omission is a key. Now I know the paper maps well enough to get meaning out of the images, but not all of you are so fortunate. Can anyone more knowledgeable than me tell me how to display the map key in Google Earth?

So, how better to show what I am going on about than to show you the WoGE images from Britain alongside their Geological maps?

WoGE #223 showed a syncline in Carboniferous sandstones/shales alongside obvious quarries in white limestone. The pattern is very clear in the map: