from green to red color depend on percentage

I have a poll system and I want answers for this poll to be colored. For example: If it's 10% it would be red, if 40% it would be yellow and if 80% it would be green, so I want my javascript code to use the rgb colors to make a color according to the given percentage.

function hexFromRGB(r, g, b) {
    var hex = [
        r.toString( 16 ),
        g.toString( 16 ),
        b.toString( 16 )
    ];
    $.each( hex, function( nr, val ) {
        if ( val.length === 1 ) {
            hex[ nr ] = "0" + val;
        }
    });
    return hex.join( "" ).toUpperCase();
}  

Now I want hex from percent.