Are American food colourings weaker than in other countries? I was looking at baking a yet-to-be-determined-colour velvet cake, and happened upon a recipe for blue velvet cake: http://bakebakebake.livejournal.com/3342197.html

This calls for two tablespoons of food colouring!  The food colouring I am most familiar with is stuff like McCormick's, which is generally measured by the drop.  Generating an entire tablespoon of a single colour would probably require several packets' worth.

Am I misunderstanding something?  Are the comparative strengths the same and you just need a heck of a lot of colouring to make a cake that dark?  Or is the American stuff a lot weaker and I'd only need the 4-5 drops I would expect from a recipe?
The simple answer is: No.

First of all the recipe says 1 tablespoon of blue food coloring. This is pretty typical for a velvet cake. In fact it's actually less than I would expect. This is because the original color is dark brown from the cocoa powder. To cover that up and turn it into a different color requires a lot of food coloring. 

If you take a look at these standard red velvet cakes, you will see that they ask for 1 ounce food coloring. And 1 fluid ounce is equivalent to 2 tablespoons. 


http://allrecipes.com/recipe/red-velvet-cupcakes-3/detail.aspx
http://allrecipes.com/recipe/red-velvet-cake-vi/detail.aspx
http://allrecipes.com/recipe/red-velvet-cake-iii/detail.aspx