symbols changing color

[John Bolster]

Hi all,

I defined a gif image as an interstate shield used in an annotation layer.
Now when I zoom in and out the color of the shields change on the output
map. The bulk of each shield should be pure blue, yet it becomes purple
sometimes and a light blue other times. They vary when I change the line
color of the underlying interstate line layer and also when I turn on and
off other layers (county lines and place polygons). Below are how my symbol
and annotation layer are defined. I can't see how mapserver is changing the
color of the gif--any suggestions on how I can get it to stay the same color
at all scales?

MapServer version 4.2.2 OUTPUT=GIF OUTPUT=PNG OUTPUT=JPEG OUTPUT=WBMP
SUPPORTS=FREETYPE INPUT=TIFF INPUT=EPPL7 INPUT=JPEG INPUT=SHAPEFILE

Thanks in advance,
John Bolster

    SYMBOL
        NAME 'int'
        TYPE pixmap
        IMAGE "./intsh.gif"
    END

    LAYER
      NAME intlabels
      GROUP "hwy"
      TYPE annotation
      STATUS off
      DATA nhpn
      PROJECTION proj=latlong END
      CLASSITEM 'type'
      LABELITEM 'num'
      LABELMAXSCALE 4000000
      CLASS
        EXPRESSION "I"
        COLOR 0 0 0
        SYMBOL "int"
        LABEL
          SIZE tiny
          POSITION CC
          BUFFER 2
          MINDISTANCE 200
          COLOR 255 255 255
        END
      END
    END