If you have some guarantee that caramel has not been added (i.e. the whisky was bottled by the SMWS or by some other independent bottler who makes a point of not colouring the whisky), then colour can sometimes
be worth paying attention to.
In these cases, it can give you clues or hints as to whether it was matured in a bourbon or sherry cask, and sometimes give an indication as to how old the whisky might be.
I once had a 16yo Ardbeg from the SMWS that was the palest of pale white wines. Yes, it was paler than mr_a_non weak urine!
And yet - on both the nose and the palate - it was one of the most spectacular Islay's I've ever tried.
However, I don't pay much attention to colour with the majority of OB's, and certainly not with blends, because I know caramel has had more of an influence than anything else.
A very cheap blend that seems to be popular here in Australia is "The Black Douglas". It retails for about $23, which is less than 10GBP, or roughly US$16. I understand it to be approximately 75/25 grain to malt ratio, and the whiskies are 3 to 5 years old. Yet it's darker than the nearly all of the aged single malts, including the 18yo Macallan!!