“What is wrong with your beer?” he said. “It’s orange!”
And I thought: yes, indeed, why? I mean, beer is usually a yellowish brown. But then I remembered: brown and orange are really in the same family of colors – only brown is darker. Try it: choose a nice brown color in photoshop. Now drop on a curves layer and brighten it. As it brightens, you’ll see it go in stages from brown, to light brownish, to an orangish, to a yellow. Mess with it a little more (darken the shadows), and you’ll get a true orange – even red, if you take it far enough.
When photographing beer, if the strobe hits the bottle dead on (in this case from beneath), it’ll light it up – essentially lightening up the browns in the beer. In beer the browns are already warm & on the orange side, so it lightens them up – to a full orange.
The photo to the right/top of this post is the exact photo that started this. Note the hues of the oranges – the closer to the light source, the more yellowish it is – the higher up, the darker – until the neck of the bottle draws light in to itself again.