The point was meant as a historical one about where the custom of colouring stemmed from. Obviously whisky aficionados like ourselves appreciate that there will be variations of colour depending on cask type, age etc so I totally agree with you on that but the Single Malt Whisky market was and still is only a small part of the Industry's business and it is something we over look easily and the influence that the Blended Whisky business has on all of the industry.
So what one must remember is within the whole whisky drinking sector we are a very small community and that 90% of Scotch sold is blended and the vast majority of that is in the mass produced category. Further not many of your average blend drinkers are going to be too worried if their bottle of "Glen Tartan" is coloured or not. However if it was suddenly uncoloured and bottled in it's natural straw yellow state I think you may find that people may opt for the golden brown "McALISTER's Pish" beside it.

As the majority of Scotch blends by Volume are non age stated you can be sure they are all being coloured. And because this has been an industry standard for decades it is ingrained in people that whisky should have an "acceptable" colour. This of course had been rife in the Single Malt market too but it is slowly but surely changing.
Colouring as a marketing strategy is basically the norm ...
Just to show you prime examples ... the top selling scotch blend is Johnnie Walker with 2011 retail sales value of $5.24 billion. Compared to the top selling Single Malts of Glenfiddich at $435 million & The Glenlivet at $330 million which is 8% & 6% of JW total sales respectively or 15% combined. Of which I think both of their entry level products (highest Volume sales wise) are coloured also ?!?!?!? And if you take the entire drinks market JW is the number 2 spirit brand in the world where Glenfiddich comes in at 61 & Glenlivet 90
And here is a list of of the top 25 whisk(e)y brands in 2010 where you will only notice that the above 2 malts are the only entries and the list is dominated by scotch blends. Strip out all bar scotch and you find 14 of the 16 scotch brands are blends.
1 JOHNNIE WALKER
2 JACK DANIEL’S
3 CHIVAS REGAL
4 BALLANTINE’S
5 JIM BEAM
6 DEWARS
7 J & B
8 CROWN ROYAL
9 JAMESON
10 GRANTS
11 FAMOUS GROUSE
12 BELL’S
13 CANADIAN CLUB
14 SEAGRAM’S 7 CROWN
15 GLENFIDDICH
16 TEACHER’S
17 MAKER’S MARK
18 BLACK VELVET
19 100 PIPERS
20 CANADIAN MIST
21 CLAN CAMPBELL
22 WILLIAM LAWSON’S
23 CUTTY SARK
24 CLAN MACGREGOR
25 THE GLENLIVET