日: 2015年3月27日

.rainbow {
  background: -moz-linear-gradient(left,
    rgba(255,0,0,0.2),
    rgba(255,69,0,0.2),
    rgba(255,255,0,0.2),
    rgba(0,128,0,0.2),
    rgba(0,0,255,0.2),
    rgba(75,0,130,0.2),
    rgba(238,130,238,0.2)
  );
  background: -webkit-gradient(linear, left center, right center,
    from(rgba(255,0,0,0.2)),
    color-stop(14%, rgba(255,69,0,0.2)),
    color-stop(28%, rgba(255,255,0,0.2)),
    color-stop(42%, rgba(0,128,0,0.2)),
    color-stop(56%, rgba(0,0,255,0.2)),
    color-stop(70%, rgba(75,0,130,0.2)),
    to(rgba(238,130,238,0.2))
  );
}

ちょい薄い
はっきり　こいつに　テキストシャドー足す

.rainbow {
background: -moz-linear-gradient(left, red, orange, yellow, green, blue, indigo, violet);
background: -webkit-gradient(linear, left center, right center, from(red), color-stop(14%, orange), color-stop(28%, yellow), color-stop(42%, green), color-stop(56%, blue), color-stop(70%, indigo), to(violet)); }

.text_shadow{	
	text-shadow: #000000 1px 1px 3px; /* FireFox, Webkit, Opera */
-ms-filter:"progid:DXImageTransform.Microsoft.DropShadow(color=#000000,offx=1,offy=1)"; /* IE8 */
display:block; /* IE */
}

いま３

background: linear-gradient(-45deg, red, orange, yellow, green, blue, indigo, violet);