can i have flashwindow effect to be applied on a VCL Tbutton Control ?
Not by default, but you can manually enable the BS_OWNERDRAW style on it, and then intercept WM_DRAWITEM messages sent to it. Then you can make it look however you want.
Or, simply use a different Button control that supports custom coloring, like TBitBtn (which already has the BS_OWNERDRAW style) or TSpeedButton.