设置UIBarButtonItem色调始终显示默认颜色

Question

我有一个IBAction响应我想用来更改图标显示颜色的选择器。我在Interface Builder中设置了darkGrayColor作为色调，但是当通过代码更改tintColor时，色调总是变为默认颜色，使图标变为白色。

UIColor *dayColor = [UIColor darkGrayColor];
UIColor *nightColor = [UIColor lightGrayColor];

dayMode = !dayModeSwitch.on;
if (dayMode) {
    [tocButton setTintColor:dayColor];
    [actionButton setTintColor:dayColor];
    [searchButton setTintColor:dayColor];
} else {
    [tocButton setTintColor:nightColor];
    [actionButton setTintColor:nightColor];
    [searchButton setTintColor:nightColor];
}