Prometheus

/click CompactRaidFrameManagerDisplayFrameLeaderOptionsRaidWorldMarkerButton
/click DropDownList1Button1

will give you blue

/click CompactRaidFrameManagerDisplayFrameLeaderOptionsRaidWorldMarkerButton
/click DropDownList1Button2

will give you green   (change the number on the end for the appropriate colour)

1. MarkSquare (“blue“)
2. MarkTriangle (“green)
3. MarkDiamond (“purple“)
4. MarkCross (“red“)
5. MarkStar (“yellow“)

source: http://wowhats.wordpress.com/2011/02/14/binding-raid-marks-and-world-markers/