This is a term used when someone turns red (blushes) because they are embarrassed.
A beet is a red "food source," so when people say red as a beet, they mean the person is either really embarrassed (blushing) or something to that affect.
got angry
This is not an idiom. When you see AS ___ AS ___, you are looking at A Simile. This one is comparing something to the red color of a turkey's wattle.
Radish
The common name for a beet is a red beet or simply a beet.
The homophone for "beat" that has the same meaning is "beet". They sound the same but are spelled differently and mean different things.
Beet juice.
In debt. Its antithesis, "in the black," refers to having a balanced budget.
It means to be patriotic (by reference to flying the flag).
It is red tape.
beet, beat
"Beet" and "beat" are homophones that can represent a tired red vegetable.