If an unpleasant meal has left you feeling grumpy and looking green, you're bilious in several senses of the word. This adjective can mean both "troubled by indigestion" and "irritable," and it can also be used to suggest a sickly green shade.
The wonderfully descriptive word bilious comes from the root bile, which is a foul green fluid made in the liver and stored in the gall bladder — a fact that helps us picture something described as bilious as being really foul. Because of the connection with bile, we often refer to something that's an ugly shade of green as being bilious. Of course, the word can also be more kindly applied to someone who has a liver or gall bladder disorder.