At the Am chords, especially in the intro, it's nice to add a little riff on the G string:
G |-2--2-2-2-4-2-0-2--|
In the last bar of the line while you're playing the chord.
The chords are exactly the same throughout, so I only bothered to write them in 
for the first couple of verses.
Enjoy!

Capo at 2

Intro:
Em - - -
Em G Am -
Em G C -
Em G Am -
Em G D -

Em                         G                            Am
Sweep up, little sweeper boy, it's you who's got the wig on here
Em                        G                      C
Sweep up, little sweeper boy, sweep up
Em                   G                Am
Yellow is the color of my true love's crossbow
Em                  G                     D
Yellow is the color of the sun

Em                         G          Am               
And black is the color of a strangled rainbow
Em                G                 C
That's the color of my loss
Em                   G              Am
Black is the color of my true love's arrow
Em                G                         D
Just the color of human blood

You got a shot of shampoo 
Though it was made thirty years ago
Yeah you still got a shot of shampoo
Though you were made twenty years ago

(Harmonica solo, same chords repeat)

Speak up, little sweeper boy, they are hard of hearing
Anything that anyone has to say
I say yellow is the color of my true love's crossbow
Yellow like the color of the sun

Well black is the color of a strangled rainbow
Just the color of my loss
Black is the color of my true love's arrow
Exactly the color of my blood   

But I don't want to die I'll ever die tomorrow maybe
Above a near perfect square of sky
You are worth your weight in gold, you are worth your weight in sorrow baby
Though you will never know why