The following VBA example exports the current page to a GIF image and ensures that the color blue is in the resulting palette:
Sub Test()
Dim pal As New StructPaletteOptions
Dim flt As ExportFilter
pal.NumColors = 10
pal.PaletteType = cdrPaletteOptimized
pal.ColorSensitive = True
pal.TargetColor = RGB(0, 0, 255)
pal.Importance = 200
pal.Lightness = 300
pal.ToleranceA = 100
pal.ToleranceB = 100
Set flt = ActiveDocument.ExportBitmap("C:\Temp\img.gif", cdrGIF, , cdrPalettedImage, PaletteOptions:=pal)
flt.Finish
End Sub