To change the backgroung color of my menu in #ffffff and Menu Text in #000000

Good Morning

My website Theme Is FOCUS .

I find this code in the forum ,

#masthead {

background: #000;

background-image: -webkit-gradient(linear, left bottom, left top, from(#000), to(#000));

background-image: -moz-gradient(linear, left bottom, left top, from(#000), to(#000));

background-image: -ms-gradient(linear, left bottom, left top, from(#000), to(#000));

background-image: -o-gradient(linear, left bottom, left top, from(#000), to(#000));

color: #FFF;

}

I put it on my Custom CSS , it does not work .

Could you please tell me what is wrong ?

Thanks for your help .

Best regards .