XF 1.3 Styling issue on IE8 "forget password" overlay

I'm trying to give my "forget password" overlay a red background color with this code

.xenOverlay .xenForm, .xenOverlay .formOverlay, .xenOverlay > .section, .xenOverlay > .sectionMain
background-color: red !important;
It works well in almost all browsers but IE 8 (don't know about other IE, I'm using IE 8)

In IE8, the colour's displayed as a brownish red, as if there is a brown semi-transparent layer over the "forget password" already-red-overlay .

Any help for this issue , please ?

thx :)