PNG generation ignoring color

[Chris Spencer]

How do you retain note color for PNG and SVG generation?

I have the following Lilypond file test.ly:

\version "2.18"
color = #(define-music-function (parser location color) (string?) #{
        \once \override NoteHead #'color = #(x11-color color)
        \once \override Stem #'color = #(x11-color color)
        \once \override Rest #'color = #(x11-color color)
        \once \override Beam #'color = #(x11-color color)
     #})

\header {
 tagline = ""
  title = "Test1"

  }

\score  {

      << \new Staff  = xawdxfwebzffzxy { \key a \major
             \time 4/4
             r 2
             \color "#00FF00" e' 4
             \color "#00FF00" e' 4
             \bar "|"  %{ end measure 1 %}
             \color "#00FF00" fis' 4
             \color "#00FF00" e' 2.
             \bar "|"  %{ end measure 2 %}
             r 2
             \color "#00FF00" fis' 4
             \color "#00FF00" e' 4
             \bar "|"  %{ end measure 3 %}
             \color "#00FF00" fis' 4
             \color "#00FF00" a' 2.
             \break
             \bar "|"  %{ end measure 4 %}
             r 2
             \color "#00FF00" b' 4
             \color "#00FF00" b' 4
             \bar "|"  %{ end measure 5 %}
             \color "#00FF00" cis'' 4
             \color "#00FF00" b' 2.
             \bar "|"  %{ end measure 6 %}
             \color "#00FF00" fis' 4
             \color "#00FF00" fis' 4
             \color "#00FF00" fis' 4
             \color "#00FF00" e' 4
             \bar "|"  %{ end measure 7 %}
             \color "#00FF00" fis' 4
             \color "#00FF00" a' 2.
             \break
             \bar "|"  %{ end measure 8 %}
             r 2
             \color "#00FF00" e' 4
             \color "#00FF00" e' 4
             \bar "|"  %{ end measure 9 %}
             \color "#00FF00" fis' 4
             \color "#00FF00" e' 2.
             \bar "|"  %{ end measure 10 %}
             \color "#00FF00" fis' 4
             \color "#00FF00" a' 4
             \color "#00FF00" a' 4
             \color "#00FF00" cis'' 4
             \bar "|"  %{ end measure 11 %}
             \color "#00FF00" a' 1
             \break
             \bar "|"  %{ end measure 12 %}
             \color "#00FF00" b' 4
             \color "#00FF00" b' 4
             \color "#00FF00" b' 4
             \color "#00FF00" b' 4
             \bar "|"  %{ end measure 13 %}
             \color "#00FF00" cis'' 4
             \color "#00FF00" b' 2.
             \bar "|"  %{ end measure 14 %}
             \color "#00FF00" fis' 4
             \color "#00FF00" a' 4
             \color "#00FF00" a' 4
             \color "#00FF00" b' 4
             \bar "|"  %{ end measure 15 %}
             \color "#00FF00" a' 2
             \break
             \bar "|."  %{ end measure 16 %}
              }


        >>

  }

\paper {
  indent = 0\cm
}
\layout {
  \context {
    \RemoveEmptyStaffContext
    \override VerticalAxisGroup #'remove-first = ##t
  }
 }

and although I've specified all notes be green, running `lilypond
--png test.ly` results in a black and white image.

Why is this? Why are the color statements being ignored?

Regards,
Chris