Inherited bgcolor of a BUTTON no reaction

if I set the bgcolor of a inherited button (programaticaly during runtime), I cant’ see any reaction, but
if I set (for example) the toolTipText of the same button, I see the new tooltip on the UI.

Is this a bug or any other reasons for

	...
	...
	var oEl = oFrm.elements	
	oEl.but_such.bgcolor	= '#ff0000' 				//   NOT ok, no different colour to see
	oEl.but_such.toolTipText = 'any Test-Text'		// this is working
	...
	...

Thank you for help

are you sure that the button is not transparent?

Yes, you are right ! This is a double :oops: :oops: