Highlight onDraw

 ..
     highLightPaint.color = ContextCompat.getColor(context, R.color.highlight_color)
     highLightPaint.style = Paint.Style.FILL
     highLightPaint.isAntiAlias = true
 ..
 
 override fun onDraw(canvas: Canvas) {
        super.onDraw(canvas)
        drawVerticalLines(canvas)
        drawHorizontalLines(canvas)
        
        if (touching) {
            drawHighlightRectangle(canvas)
        }
    }
    
    private fun drawHighlightRectangle(canvas: Canvas) {
        canvas.drawRect(squares[rectIndex.first][rectIndex.second], highLightPaint)
    }