Thank Jim! I was so close to solve it myself but had the TextField in a container. This means you need to get the window from self.window.handle instead of self.handle. Gosh! 
declare sub setInsertionPointColor lib CocoaLib selector “setInsertionPointColor:” (obj_id as Ptr, aColor as Ptr)
declare function blackColor lib CocoaLib selector “blackColor” (ob_id As Ptr) As Ptr
declare function fieldEditorForObject lib CocoaLib selector “fieldEditor:forObject:” (ob_id As Ptr, flag as boolean, f as ptr) As Ptr
dim e as ptr = fieldEditorForObject( ptr(self.Window.Handle), true, ptr(me.Handle) )
if e<>nil then
setInsertionPointColor( e, blackColor(NSClassFromString(“NSColor”)) )
end if
As an extension for the TextField:
[code]Sub caretColor(extends t as TextField, assigns c as color)
declare sub setInsertionPointColor lib CocoaLib selector “setInsertionPointColor:” (obj_id as Ptr, aColor as Ptr)
declare function blackColor lib CocoaLib selector “blackColor” (ob_id As Ptr) As Ptr
declare function fieldEditorForObject lib CocoaLib selector “fieldEditor:forObject:” (ob_id As Ptr, flag as boolean, f as ptr) As Ptr
declare function colorFromRGBA lib CocoaLib selector “colorWithCalibratedRed:green:blue:alpha:” (class_id as Ptr, red as CGFloat, green as CGFloat, blue as CGFloat, alpha as CGFloat) as Ptr
declare Function NSClassFromString Lib CocoaLib (aClassName as CFStringRef) As Ptr
dim col as ptr = colorFromRGBA(NSClassFromString(“NSColor”),c.Red/255,c.Green/255,c.Blue/255,(255-c.alpha)/255 )
if col<>nil then
dim e as ptr = fieldEditorForObject( ptr(t.TrueWindow.Handle), true, ptr(t.Handle) )
if e<>nil then
setInsertionPointColor( e, col )
end if
end if
End Sub[/code]