All scotch whisky (SM or blended) is regulated by Scottish law that no colourings, additives etc can be added. Virtually every single whisky that CRC don't recommend are allowed without question by KLBD as they are not matured in sherry casks etc. See link:
http://www.kosher.org.uk/article/are-all-whiskies-kosher
Hence I find it puzzling that CRC 'don't recommend' so many of those whiskies eg Abelour, Glengoyne etc. No justifiable reason not to do so.
I think you are mistaken. colorings are allowed in scotch (and many dark whisky's use coloring). coloring is not allowed in american bourbon.
I find the scotch whisky lists to be quite lacking and uninformative. They do not give a comprehensive look at whisky's, rather they look at "popular" ones. Glengoyne and Aberlour (as do most macallan's) use ex-sherry casks. Ask your LOR whether that presents an issue for you.
Some whisky's that my ultra ortho friends serve and shuls and catering halls serve (eg glenlivet, johnnie have a hint of sherry in the taste for some experts).
What is bothersome for me is by the standard that people are putting on ex-sherry casks, for kashrus, how can you drink any blends? a blend can have dozens and dozens of scotches from hundreds or barrels, hogsheads, casks, and stills, how can one know what was used and how anything was cleaned for a blend?