如何通过kotlin代码在android中更改笔画颜色？

<com.example.myapp.CanvasView
    android:id="@+id/canvasView"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

import android.content.Context
import android.graphics.Canvas
import android.graphics.Color
import android.graphics.Paint
import android.view.View

class CanvasView(context: Context) : View(context) {
    private val paint = Paint()

    override fun onDraw(canvas: Canvas) {
        super.onDraw(canvas)
        
        // 设置画笔颜色为红色
        paint.color = Color.RED
        
        // 绘制图形和笔画
        // ...
    }
}

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        
        val canvasView = findViewById<CanvasView>(R.id.canvasView)
        
        // 更改画笔颜色为蓝色
        canvasView.paint.color = Color.BLUE
        
        // 触发重绘
        canvasView.invalidate()
    }
}