js画布画机器猫调色

问题遇到的现象和发生背景

机器猫全蓝

问题相关代码，请勿粘贴截图
<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title></title>
    </head>
    <style type="text/css">
        div{
            text-align: center;
        }
        canvas{
            border: 1px solid red;
        }
    </style>
    <body>
        <div id="">
            <canvas id="" width="500" height="600"></canvas>
        </div>
    </body>
    <script type="text/javascript">
        var canvas=document.getElementsByTagName('canvas')[0]
        var b= canvas.getContext('2d')
        function y(x,y,z,c){
            b.beginPath()
            b.arc(x,y,z,0,2*Math.PI,false)
            b.stroke()
            b.fillStyle=c
            b.fill()
            b.closePath()
        }
        y(250,250,220,'#0bbee7')//头
        y(250,184,16,'#c13f03')//鼻子
        y(258,180,6,'#ffffff')
        function a(x,y,x1,y1){
            b.beginPath()
            b.moveTo(x,y)
            b.lineTo(x1,y1)
            b.stroke()
            b.closePath()
        }
        function e(x,y,x1,y1,x2,y2){
            b.beginPath()
            b.moveTo(x,y)
            b.quadraticCurveTo(x1,y1,x2,y2)
            b.stroke()
            b.closePath()
        }
        function s(x,y,x1,y1,x2,y2,x3,y3){
            b.beginPath()
            b.moveTo(x,y)
            b.bezierCurveTo(x1,y1,x2,y2,x3,y3)
            b.stroke()
            b.closePath()
        }
        //嘴巴
        a(250,200,250,350)
        e(130,300,250,400,370,300)
        //眼睛
        y(230,160,6,'black')
        y(270,160,6,'black')
        a(250,105,250,155)
        a(180,105,180,155)
        a(320,105,320,155)
        s(180,105,180,65,250,65,250,105)
        s(320,105,320,65,250,65,250,105)
        s(180,155,180,185,250,185,250,155)
        s(320,155,320,185,250,185,250,155)
        //脸轮廓
        s(180,125,30,145,30,430,250,430)
        s(320,125,470,145,470,430,250,430)
        //胡须
        a(200,220,140,200)
        a(200,240,140,240)
        a(200,260,140,280)
        a(300,220,360,200)
        a(300,240,360,240)
        a(300,260,360,280)
    </script>
</html>
运行结果及报错内容

img

我的解答思路和尝试过的方法
我想要达到的结果

img

在画脸的位置设置颜色为白色