Interesting thread this... I find this a very flawed example, if you want to test the 2 drops of angostura versus 4 drops of 1:1 angostura:water don't use a drink that has a variable amount of dilution from ice! Unless you can guarantee that you used the same volume of consistent quality ice at exactly the same temperature etc etc. I would also contend that the colour would be exactly the same (once you stir it in of course) for the same reasons as the taste would be exactly the same. The second you mix the drink the ice is obviously diluting everything, including the bitters solutions, and when you're using only 1-2 mls of bitters, in a glass filled with ice, it's not going to take much of a difference in the melting rate of the ice in the two drinks to totally skew the results. To test it in a cocktail situation surely you would have to exclude ice from the equation since we can never have total control over it, and at these quantities it's too big a factor. It may not be ideal but wouldn't using chilled ingredients for, say, a Manhattan and chilled water to dilute be a much better way? In which case yes, the two would theoretically taste slightly different (as one will have 2 drops more water to dilute the tasteful parts) but i defy anyone to be able to taste the difference between the two. Anyway, that's all kind of irrelevant to the original discussion. I won't claim to have all that much knowledge about making bitters, is simply diluting pre-made bitters with water to get a new bitters with half the ABV really representative of how you would go about making two different strengths of the same flavour bitters? If so then I don't see how there is even a debate here.. And it would be against the law to sell it I think. Even to give it away in a bar would be pretty risky legally speaking I'd imagine, but whatever you get up to in the privacy of your own home is nobody's business but your own...