I have override /libs/cq/gui/components/authoring/editors/clientlibs/core/css/overlay.less to apps/cq/gui/components/authoring/editors/clientlibs/core/css/overlay.less. and i have change changed background color like below.

/* placeholder */

.cq-Overlay--placeholder {

    color: rgba(0,0,0,.3);

    border-color:  rgba(0,0,0,.3);

  /* background-color: rgba(255,255,255,.05);*/

     background-color: rgba(255,255,255,.25);

    border-style: solid;

    border-width: 0.125rem;

    margin: -0.125rem;

}

Still i am getting old values. what is the recommended way to override aem ootb stylesheet?

Thanks,

Kiran