对于这个改变色差的方法，以前一直纠结，一直想凑合。。今天终于是凑合不起来了。各种试各种改都达不到要求。最后终于找到解决办法。下面贴出解决方案，实际上就是给navbar添加个分类。

import "UINavigationBar+BackgroundColor.h"

static char overlayKey;

@implementation UINavigationBar (BackgroundColor)

• (UIView *)overlay{
  return objc_getAssociatedObject(self, &overlayKey);
  }

• (void)setOverlay:(UIView *)overlay{
  objc_setAssociatedObject(self, &overlayKey, overlay, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
  }

• (void)KPSetBackgroundColor:(UIColor *)backgroundColor{
  backgroundColor = _COLOR_RGB(0xe72a2d);

  if (!self.overlay) {
  [self setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];

    UIView *backgroundView = [self KPGetBackgroundView];
    self.overlay = [[UIView alloc] initWithFrame:backgroundView.bounds];
    self.overlay.userInteractionEnabled = NO;
    self.overlay.autoresizingMask = UIViewAutoresizingFlexibleWidth|UIViewAutoresizingFlexibleHeight;
    
    [backgroundView insertSubview:self.overlay atIndex:0];
  

  }
  self.overlay.backgroundColor = backgroundColor;
  }

• (UIView*)KPGetBackgroundView{
  //iOS10之前为 _UINavigationBarBackground, iOS10为 _UIBarBackground
  //_UINavigationBarBackground实际为UIImageView子类，而_UIBarBackground是UIView子类
  //之前setBackgroundImage直接赋值给_UINavigationBarBackground，现在则是设置后为_UIBarBackground增加一个UIImageView子控件方式去呈现图片

  if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 10.0) {
  UIView *_UIBackground;
  NSString *targetName = @"_UIBarBackground";
  Class _UIBarBackgroundClass = NSClassFromString(targetName);

    for (UIView *subview in self.subviews) {
        if ([subview isKindOfClass:_UIBarBackgroundClass.class]) {
            _UIBackground = subview;
            break;
        }
    }
    return _UIBackground;
  

  }
  else {
  UIView *_UINavigationBarBackground;
  NSString *targetName = @"_UINavigationBarBackground";
  Class _UINavigationBarBackgroundClass = NSClassFromString(targetName);

    for (UIView *subview in self.subviews) {
        if ([subview isKindOfClass:_UINavigationBarBackgroundClass.class]) {
            _UINavigationBarBackground = subview;
            break;
        }
    }
    return _UINavigationBarBackground;
  

  }
  }

pragma mark - shadow view

• (void)KPHideShadowImageOrNot:(BOOL)bHidden{
  UIView *bgView = [self KPGetBackgroundView];

  //shadowImage应该是只占一个像素，即1.0/scale
  for (UIView *subview in bgView.subviews) {
  if (CGRectGetHeight(subview.bounds) <= 1.0) {
  subview.hidden = bHidden;
  }
  }
  }

@end
self.navigationController.navigationBar.translucent = YES;
要用的直接贴上去就可以。

http://www.cocoachina.com/ios/20161214/18353.html