iOS: UIColor System Colors

ios_uicolor_system_colors.m

UIColorSystemColors has these values to choose from.

@interface UIColor (UIColorSystemColors)
+ (UIColor *)lightTextColor;                // for a dark background
+ (UIColor *)darkTextColor;                 // for a light background
+ (UIColor *)groupTableViewBackgroundColor;
+ (UIColor *)viewFlipsideBackgroundColor;
+ (UIColor *)scrollViewTexturedBackgroundColor __OSX_AVAILABLE_STARTING(__MAC_NA, __IPHONE_3_2);
+ (UIColor *)underPageBackgroundColor __OSX_AVAILABLE_STARTING(__MAC_NA, __IPHONE_5_0);
@end

If you want to use any of these UIColors to color your background. You can achieve it using a UIColor class object. See example below on changing window background color with texture.

mainWindow = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
mainWindow.backgroundColor = [UIColor scrollViewTexturedBackgroundColor]; // Window background color