Got it..

The .bmp was converted to a base64 string for ease of demo (iirc there were no attachments possible on the german board). If you use a Bitmap from file you will have to alter the Code to $Bitmap = $System.Bitmap([path\]filename)

The Original bmp can be found attached (Notice the Black/White Symbol)
Be aware that the movable Icon was attached to a Toolbutton that does nothing. It was the only way I was able to get that transparent thing going $\:D$
The movability is just for fun and giggles and maybe educational purposes.

Code:

Break on

$System = CreateObject("Kixtart.System")

$Bitmap = $System.Bitmap.FromBase64String(YingYangImageString())

$frm = $System.Form()
$frm.ClientSize = $System.Size(400, 300)
$frm.Text = "TransparentColor Demo"
$frm.BackColor = "KiXtart"

$ImageList = $System.ImageList()
$ImageList.ImageSize = 111, 109
$ImageList.TransparentColor = "white"
$ImageList.Images.AddStrip($Bitmap)

$btn1 = $frm.Toolbutton
$btn1.Size = 111, 109
$btn1.FlatStyle = 0
$btn1.BorderStyle = 0
$btn1.BackColor = "Transparent"
$btn1.Icon = $ImageList.Images(0)
$btn1.OnMouseDown = "$$x = $$btn1.MouseX $$y = $$btn1.MouseY"
$btn1.OnMouseMove = "MouseMove()"

$btn1.Center


$frm.Show

While $frm.Visible
 $=Execute($frm.DoEvents)
Loop 

Exit 1 

function YingYangImageString()
$YingYangImageString =

"Qk0OBwAAAAAAAD4AAAAoAAAAbwAAAG0AAAABAAEAAAAAAAAAAAAAAAAAAAAAAAIAAAACAAAA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"

endfunction

Function MouseMove()

   If $btn1.MouseButton = 1
      $frm.BeginUpdate
      $btn1.Location  = $frm.MouseX - $x , $frm.MouseY - $y
      $frm.EndUpdate
   EndIf

EndFunction

Hope this helps a little bit