...
A fruit salad composed of one fruit each: lemon, grapefruit, unripe pineapple, tamarind pulp, and unripe passionfruit pulp minus the pips.
Can't say I'd want to eat it.
Sour emotions can include anger, envy, disappointment and disillusionment.
Envy is often portrayed as yellow.
So taking one element from the list of emotions, and one element from the list of colours,
the axiom of choice is yellow with envy.
