Color a UIImage with transparency (in a category).

UIImage+Color.m

-(UIImage *)imageWithTint:(UIColor *)color {
    // Setup the color
    CGFloat redColor;
    CGFloat greenColor;
    CGFloat blueColor;
    CGFloat alphaColor;
    
    [color getRed:&redColor green:&greenColor blue:&blueColor alpha:&alphaColor];
    
    // First get the image into your data buffer
    CGImageRef imageRef = [self CGImage];
    NSUInteger width = CGImageGetWidth(imageRef);
    NSUInteger height = CGImageGetHeight(imageRef);
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    unsigned char *rawData = (unsigned char*) calloc(height * width * 4, sizeof(unsigned char));
    NSUInteger bytesPerPixel = 4;
    NSUInteger bytesPerRow = bytesPerPixel * width;
    NSUInteger bitsPerComponent = 8;
    CGContextRef context = CGBitmapContextCreate(rawData, width, height,
                                                 bitsPerComponent, bytesPerRow, colorSpace,
                                                 kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
    
    
    CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);
    CGContextRelease(context);
    
    // Now your rawData contains the image data in the RGBA8888 pixel format.
    for (int xx = 0; xx < width; xx++) {
        for(int yy = 0; yy < height; yy++) {
            int byteIndex = (bytesPerRow * yy) + xx * bytesPerPixel;
            CGFloat alpha = (rawData[byteIndex + 3] * 1.0) / 255.0;
            
            rawData[byteIndex] = MAX(0,MIN(255,(int)(redColor*alpha * 255.0)));
            rawData[byteIndex+1] = MAX(0,MIN(255,(int)(greenColor*alpha * 255.0)));
            rawData[byteIndex+2] = MAX(0,MIN(255,(int)(blueColor*alpha * 255.0)));
        }
    }
    
    context = CGBitmapContextCreate(rawData, width, height,
                                     bitsPerComponent, bytesPerRow, colorSpace,
                                     kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
    CGColorSpaceRelease(colorSpace);
    CGImageRef newImage = CGBitmapContextCreateImage(context);
    
    CGContextRelease(context);
    free(rawData);
    
    UIImage * resultUIImage = [UIImage imageWithCGImage:newImage scale:2 orientation:0];
    CGImageRelease(newImage);
    
    return resultUIImage;
}