Hi,
Yes — the page looks darker because of this overlay:

.home-wrap .ri-grid:after { opacity: 0.6; background:#111; }

To make the page brighter, you can simply reduce the opacity (recommended). Add this CSS (or edit the existing rule):

.home-wrap .ri-grid:after{
  opacity: 0.25; /* try 0.10–0.35 */
}

If you prefer an even softer bright look, you can switch the overlay to white:

.home-wrap .ri-grid:after{
  background: #fff;
  opacity: 0.10; /* try 0.06–0.18 */
}

Please clear your cache after saving (and hard refresh the page) so the change shows immediately.
Thanks