Loch Dhu ('Dark Lake' in gaelic) is a black whisky marketed by Diageo, formerly United Distillers from malt distilled at Mannochmore. Diageo don't say how the dark colour is achieved but claim it is not from caramel.
The dark colour is very striking and was described by a contributor to the malts list [cr] as
". enjoyed a dram of Loch Dhu. It has a coloring and viscosity of soy sauce, or in the same realm Sam Adams Triple Bock, and you can only every drink a single two fingers worth in a sitting. However, we all found it to have a rich, burnt flavor. It was very different than any other whisky any of us had tried before."
A second opinion [rs]:
"Loch Dhu could be regarded as a foray into the more extreme digestif market. When I tried it I was struck by how similar in character it was to the Italian digestif Amaro (also a Hungarian digestif that the name escapes me right now; something 'o....icum' I think) but without the cloying stickiness these types of drinks often have. Drank as a comparison with these drinks it was very good. Drank considering it as a single malt it was awful."
These probably sum up opinion which is sharply divided - you either like it or loathe it. Either way it is not like any other whisky.
Search Dr. Do'g's index for the history of Loch Dhu
There just might be some news about Loch Dhu in The "Scotsman" newspaper