如题所示，就是一个小tip，百度了很久都没答案，就在stackoverflow上找到了答案，方法有如下几种：
1.iOS5+ oc版：
[[UILabelappearanceWhenContainedIn:[UISearchBarclass],nil]setTextColor:[UIColorredColor]];
2.取出searcher里的textfield，再进行修改：
//取出textfield
UITextField*searchField=[searchBar valueForKey:@"_searchField"];
//改变searcher的textcolor
searchField.textColor=[UIColor redColor];
//改变placeholder的颜色
[searchField setValue：[UIColorblueColor]forKeyPath:@"_placeholderLabel.textColor"];
3.swift版
var textFieldInsideSearchBar=searchBar.valueForKey("searchField")as?UITextField
textFieldInsideSearchBar?.textColor=UIColor.whiteColor()
var textFieldInsideSearchBarLabel=textFieldInsideSearchBar!.valueForKey("placeholderLabel")as?UILabel
textFieldInsideSearchBarLabel?.textColor=UIColor.whiteColor()
以上内容参考ios - UISearchBar change placeholder color - Stack Overflow
