:nth-child(3) (selects third child)

foofy
foofy
foofy
foofy

:nth-child(0n+1) (selects first child)

foofy
foofy
foofy
foofy

:nth-child(1n+0) (selects all)

foofy
foofy
foofy
foofy

:nth-child(n+0) (selects all)

foofy
foofy
foofy
foofy

:nth-child(n) (selects all)

foofy
foofy
foofy
foofy

:nth-child(even) (also tests ':nth-child(2n)')

foofy
foofy
foofy
foofy

:nth-child(odd) (also tests ':nth-child(2n+1)')

foofy
foofy
foofy
foofy

This should be green

This should be blue

This should be orange

This should be red