I'm afraid the blueness of the Mercury's dial is just a reflection of the sky.
A better pic:
It's a bit of a mystery watch. A friend on WS has one but I've never seen another. The same year saw Sony and Safir (maybe others too ?) branded Sportsmatics, so maybe they were promotional watches.
They weren't classed as divers' watches, and the Waterproof designation was changed to Water Resistant at the end of the '60s,beginning of '70s.
I haven't come across any UK dealers, only Ebayers and it's rare (though not impossible) to find one who actually knows what they're talking about. You may be better off going for a Japanese seller, though import tax is always a risk. If you find anything you like the look of, don't be afraid to ask for advice !
And of course, once you've reached 50 posts you will have access to the Classified section of the Forum. It's all downhill for your wallet from then. Ask me how I know.