Why are Radishes Red?

Fools often ask why
Things are as they are
I choose not to try
To go quite that far

I figure it must be
Some great cosmic plan
That a bonsai can be a tree
And a woman can be a man

Still there is one great mystery
That drives me brain dead
And leaves piles of debris
Why are radishes red?

They could be pistachio
They could be lime green
They could be indigo
Know what I mean?

Johnny is a word whiz
Important ideas fill his head
But all I want to know is
Why are radishes red?