Brewer's caramel, or any form of caramel color, is very often used in bread making to colour the product without colouring the crust. Since I want to brew a very low gravity mild in the next few weeks, I had to research the topic: just subbing caramel malts or sinamar will impart a taste that was not intended to be in the recipe. A lot of English recipes seem to make heavy use of the ingredient instead of caramel malts, probably because malts are expensive and caramel color is dirt cheap.
I found a recipe for "pumpernickel color" on a message board that seems to be a homemade version of what Brupacks sells in the UK: inverted sugar burnt to hell mixed in with some water to drastically darken the color of bread without imparting a lot of flavour.
"Pumpernickel Color"
3 T sugar
1T water
Pinch cream of tartar
1/4 cup boiling water
"In a heavy saucepan over low heat, melt the sugar in the tablespoon of water. Increast the heat to medium-high, cover the pan, bring to a boil, and boil for 2 minutes. Add the cream of tartar and continue to boil, uncovered, until the sugar is almost black in color. Remove the pan from the heat. The sugar will continue cook and darken. Allow it to begin to cool. Using extreme care, add the boiling water (the sugar will boil up and may splatter). Stir to disolve, then let cool to room temperature.
Whenever you use pumpernickel color, wet the measuring spoon or cup with cold wter for easier cleanup. Soaking the saucepan and the utensils in hot water will dissolve the caramelized sugar remaining on them."