如何在swift上更改覆盖缺口区域的条染色颜色(uikit)

import UIKit

class CustomBarChartView: UIView {
    
    var data: [CGFloat] = [] {
        didSet {
            setNeedsDisplay()
        }
    }
    
    var barColor: UIColor = .blue {
        didSet {
            setNeedsDisplay()
        }
    }
    
    var gapColor: UIColor = .lightGray {
        didSet {
            setNeedsDisplay()
        }
    }
    
    override func draw(_ rect: CGRect) {
        super.draw(rect)
        
        guard !data.isEmpty else { return }
        
        let barWidth = rect.width / CGFloat(data.count)
        let maxValue = data.max() ?? 1
        
        for (index, value) in data.enumerated() {
            let barHeight = rect.height * value / maxValue
            let x = CGFloat(index) * barWidth
            let y = rect.height - barHeight
            
            // Draw the filled part of the bar
            let filledPath = UIBezierPath(rect: CGRect(x: x, y: y, width: barWidth, height: barHeight))
            barColor.setFill()
            filledPath.fill()
            
            // Draw the gap part of the bar
            let gapPath = UIBezierPath(rect: CGRect(x: x, y: rect.height - 1, width: barWidth, height: 1))
            gapColor.setFill()
            gapPath.fill()
        }
    }
}

// Usage
let barChartView = CustomBarChartView(frame: CGRect(x: 0, y: 0, width: 300, height: 200))
barChartView.data = [100, 150, 75, 200]
barChartView.barColor = .green
barChartView.gapColor = .red
view.addSubview(barChartView)