You can use different color , different font and different size text in your control(UILabel, UITextField or UItextView) by using this class method
+ (void)setMultiColorAndFontText:(NSString *)text rangeString:(NSArray *)rangeString inputView:(UITextView*) inputView font:(NSArray*) fontName color:(NSArray*) colorName
{
    inputView.layer.sublayers = nil;
    NSMutableAttributedString *mutableAttributedString = [[ NSMutableAttributedString alloc]initWithString:text];
    for (int i =0 ; i<[rangeString count]; i++)
    {
        CTFontRef  ctFont = CTFontCreateWithName((__bridge CFStringRef) [UIFont fontWithName:[fontName objectAtIndex:i] size:14.0].fontName, [UIFont fontWithName:[fontName objectAtIndex:i] size:14.0].pointSize, NULL);
        NSRange whiteRange = [text rangeOfString:[rangeString objectAtIndex:i]];
        if (whiteRange.location != NSNotFound)
        {
            [mutableAttributedString addAttribute:(NSString *)kCTForegroundColorAttributeName value:(id)[colorName objectAtIndex:i] range:whiteRange];
            [mutableAttributedString addAttribute:(NSString*)kCTFontAttributeName
                                            value:( __bridge id)ctFont
                                            range:whiteRange];
        }
    }
    CGSize expectedinputViewSize = [text sizeWithFont:[UIFont fontWithName:@"Helvetica" size:14.0f] constrainedToSize:CGSizeMake(186,100) lineBreakMode:UILineBreakModeWordWrap];
    CATextLayer   *textLayer = [[CATextLayer alloc]init];
    textLayer.frame =CGRectMake(0,4, inputView.frame.size.width,expectedinputViewSize.height+4);
    textLayer.contentsScale = [[UIScreen mainScreen] scale];
    textLayer.string=mutableAttributedString;
    textLayer.opacity = 1.0;
    textLayer.alignmentMode = kCAAlignmentLeft;
    [inputView.layer addSublayer:textLayer];
    [textLayer setWrapped:TRUE];
    [inputView setText:@""];
}
Here you can pass your text , its range , font and color as parameters. 
Example : 
[CommonFunctions setMultiColorAndFontText:@"This is a textview" rangeString:[NSArray arrayWithObjects:@"This is a",@"textview", nil] textfield:txtEmailAddress font:[NSArray arrayWithObjects:@"Arial",@"Helvetica",nil] color:[NSArray  arrayWithObjects:(UIColor *)[UIColor whiteColor].CGColor,(UIColor *)[UIColor redColor].CGColor,nil]];
It will display text with different color and different font.
Note :  In this method we have used UITextView . If you need UILabel or UITextField then you just need to change it in same way like:
UILabel
+ (void)setMultiColorAndFontText:(NSString *)text rangeString:(NSArray *)rangeString inputView:(UILabel*) label font:(NSArray*) fontName color:(NSArray*) colorName;
UITextField
+ (void)setMultiColorAndFontText:(NSString *)text rangeString:(NSArray *)rangeString inputView:(UITextField*) label font:(NSArray*) fontName color:(NSArray*) colorName;
UITextView
+ (void)setMultiColorAndFontText:(NSString *)text rangeString:(NSArray *)rangeString inputView:(UITextView*) label font:(NSArray*) fontName color:(NSArray*) colorName;
Hope it helps you.