Special style for scratch

I want to know how to apply style for scratch toolbar. This will effect to scratch but not to other apps.

Like Dan make style for Gala:

/********
 * Gala *
 *******/

.gala-workspaces-background {
 border-top: 1px solid alpha (#fff, 0.15);
 background-image: -gtk-gradient (linear,
  left top, left bottom,
  from (#1d1d1d),
  color-stop (0.07, #252525),
  to (#252525));
}