Swift等价于@Tom的答案，尽管接收RGBA Int值以支持透明度:

func colorWithHex(aHex: UInt) -> UIColor
{
    return UIColor(red: CGFloat((aHex & 0xFF000000) >> 24) / 255,
        green: CGFloat((aHex & 0x00FF0000) >> 16) / 255,
        blue: CGFloat((aHex & 0x0000FF00) >> 8) / 255,
        alpha: CGFloat((aHex & 0x000000FF) >> 0) / 255)
}

//usage
var color = colorWithHex(0x7F00FFFF)

如果你想从string中使用它，你可以使用strtoul:

var hexString = "0x7F00FFFF"

let num = strtoul(hexString, nil, 16)

var colorFromString = colorWithHex(num)

上面的几个解决方案涉及到一些不必要的nsstring使用。这个UIColor类扩展更简单更快:

+ colorWithHex:(UInt32)hex alpha:(CGFloat)alpha
{
    return [UIColor colorWithRed:((hex & 0xFF0000) >> 16)/255.0
                           green:((hex & 0x00FF00) >> 8)/255.0
                            blue:( hex & 0x0000FF)/255.0
                           alpha:alpha];
}

简单来说:

return [UIColor colorWithHex:0x006400 alpha:1.0]; // HTML darkgreen

据我所知，没有从十六进制字符串到UIColor(或CGColor)的内置转换。但是，您可以很容易地为此目的编写几个函数—例如，参见iphone开发访问uicolor组件

    //UIColorWithHexString

    static UIColor * UIColorWithHexString(NSString *hex) {
        unsigned int rgb = 0;
        [[NSScanner scannerWithString:
          [[hex uppercaseString] stringByTrimmingCharactersInSet:
           [[NSCharacterSet characterSetWithCharactersInString:@"0123456789ABCDEF"] invertedSet]]]
         scanHexInt:&rgb];
        return [UIColor colorWithRed:((CGFloat)((rgb & 0xFF0000) >> 16)) / 255.0
                               green:((CGFloat)((rgb & 0xFF00) >> 8)) / 255.0
                                blue:((CGFloat)(rgb & 0xFF)) / 255.0
                               alpha:1.0];
    }

使用

self.view.backgroundColor = UIColorWithHexString(@"#0F35C0");

Swift 2.0版本的解决方案，将处理alpha值的颜色和完美的错误处理:

func RGBColor(hexColorStr : String) -> UIColor?{

    var red:CGFloat = 0.0
    var green:CGFloat = 0.0
    var blue:CGFloat = 0.0
    var alpha:CGFloat = 1.0

    if hexColorStr.hasPrefix("#"){

        let index   = hexColorStr.startIndex.advancedBy(1)
        let hex     = hexColorStr.substringFromIndex(index)
        let scanner = NSScanner(string: hex)
        var hexValue: CUnsignedLongLong = 0

        if scanner.scanHexLongLong(&hexValue)
        {
            if hex.characters.count == 6
            {
                red   = CGFloat((hexValue & 0xFF0000) >> 16) / 255.0
                green = CGFloat((hexValue & 0x00FF00) >> 8)  / 255.0
                blue  = CGFloat(hexValue & 0x0000FF) / 255.0
            }
            else if hex.characters.count == 8
            {
                red   = CGFloat((hexValue & 0xFF000000) >> 24) / 255.0
                green = CGFloat((hexValue & 0x00FF0000) >> 16) / 255.0
                blue  = CGFloat((hexValue & 0x0000FF00) >> 8)  / 255.0
                alpha = CGFloat(hexValue & 0x000000FF)         / 255.0
            }
            else
            {
                print("invalid hex code string, length should be 7 or 9", terminator: "")
                return nil
            }
        }
        else
        {
            print("scan hex error")
       return nil
        }
    }

    let color: UIColor =  UIColor(red:CGFloat(red), green: CGFloat(green), blue:CGFloat(blue), alpha: alpha)
    return color
}

swift 2.0+。 这段代码对我来说很好。

extension UIColor {
    /// UIColor(hexString: "#cc0000")
    internal convenience init?(hexString:String) {
        guard hexString.characters[hexString.startIndex] == Character("#") else {
            return nil
        }
        guard hexString.characters.count == "#000000".characters.count else {
            return nil
        }
        let digits = hexString.substringFromIndex(hexString.startIndex.advancedBy(1))
        guard Int(digits,radix:16) != nil else{
            return nil
        }
        let red = digits.substringToIndex(digits.startIndex.advancedBy(2))
        let green = digits.substringWithRange(Range<String.Index>(start: digits.startIndex.advancedBy(2),
            end: digits.startIndex.advancedBy(4)))
        let blue = digits.substringWithRange(Range<String.Index>(start:digits.startIndex.advancedBy(4),
            end:digits.startIndex.advancedBy(6)))
        let redf = CGFloat(Double(Int(red, radix:16)!) / 255.0)
        let greenf = CGFloat(Double(Int(green, radix:16)!) / 255.0)
        let bluef = CGFloat(Double(Int(blue, radix:16)!) / 255.0)
        self.init(red: redf, green: greenf, blue: bluef, alpha: CGFloat(1.0))
    }
}

此代码包括字符串格式检查。 如。

let aColor = UIColor(hexString: "#dadada")!
let failed = UIColor(hexString: "123zzzz")

据我所知，我的代码在维护可失败条件的语义和返回可选值方面没有任何缺点。这应该是最好的答案。