Dark spirits get all of their colour from ageing in barrels, right?
Not quite.
It's permissable to add caramel to Scotch whisky, rum, and other spirits for the sake of colour and flavour consistency.

In the interests of developing an industry, this makes perfect sense. (Though some people might have an issue with the word "industry" in relation to something they're putting into their bodies.)

Drecon.dk is an incredibly eye-opening site where the brix levels of various rums are measured and the amounts of added sugar are recorded.
Brilliant.
Adding a 1/4 cup of sugar to a bottle of rum? Not so much.
Probably shouldn't be necessary.

According to author Johnny Drejer:

If you take a cheap rum, not aged very long, add some caramel colour plus sugar, and market it as a premium rum...the consumers end up with a rum that's just sweet due to the sugar added and the underlying complex rum flavours are gone because its a young rum that's missing most of the ageing process that will add complexity and smoothness to the rum. This will have an impact on the producers that spend a lot of effort/time and money in producing a premium quality rum.

Stop supporting the big guys who take shortcuts!

Interestingly, production of Bourbon Whiskey is bound by a bunch of somewhat arbitrary legislation relating to ageing, but the addition of caramel is not allowed.

The flow-on of a legal restriction such as this? You get producers like Buffalo Trace experimenting not with different species of wood, but with 96 individual trees of the same species that are coopered and filled with new-make so that oak terroir and even the effect of the part of the tree that the barrel came from are measured over a four-year study.

Wow!

Here's an excerpt from a very informative press release from this distillery:

FRANKFORT, FRANKLIN COUNTY, KY (Nov. 18, 2014) – Buffalo Trace Distillery is nearing the end of its Single Oak Project, with just one more bourbon release to go after this, in what will be a four year study of seven different variables and how they affect taste.

This release features bourbons which were all aged in barrels with the same entry proof (105), same stave seasoning, aged in the same warehouse (concrete floor), and same char level (number three). All other variables, recipe (wheat or rye), grain size, and tree cut (top or bottom of the tree) vary.

"There are many variables to consider in this project but one of the most interesting to learn more about has been tree cut," said Harlen Wheatley, master distiller. "There are four direct components that are related to wood that contribute to our bourbon flavor; hemicellulose, lignin, tannins, and the char layer. There are two major considerations when it comes to tree composition and location, and those are lignins and tannins. The top half of the tree tends to have more lignin, which contributes to the formulation of vanilla and vanilla flavor. The bottom half of the tree tends to have more tannins, which contributes to the formation of ellagic acids and tannic flavor. Tannic flavor leaves your mouth dry and delivers complexity or richness in texture."

I find this all pretty interesting. But if you're thinking about this and not dancing while you drink, well, it's only booze for thought anyway.

Footnote: Check out this bottle of unaged dark rum from Lyon Distilling in Maryland. Note the reddish colour when it's held up to the light? This is unaged cane spirit that has had home-made organic caramel added. This is very different to E150, the lab-synthesised chemical caramel. There's a familiar taste but this has layers of delicious caramel flavours - and it really highlights exactly what industrial caramel tastes like. A fun experiment from Dan Lyons, and hugely educational for us here at SPIRIT PEOPLE.