textfield click
-(void)viewWillAppear:(BOOL)animated{
      [textfieldname addTarget:self action:@selector(textFieldDidChange:) forControlEvents:UIControlEventEditingChanged];
}
return Textfiled color change
- (void)textFieldDidChange:(UITextField *)textfield{
    CALayer *border = [CALayer layer];
    CGFloat borderWidth = 2;
    border.borderColor =[UIColor colorWithRed:111.0f/255.0f green:111.0f/255.0f blue:111.0f/255.0f alpha:1.0].CGColor;
    border.frame = CGRectMake(0, textfield.frame.size.height - borderWidth, textfield.frame.size.width, textfield.frame.size.height);
    border.borderWidth = borderWidth;
    [textfield.layer addSublayer:border];
    textfield.layer.masksToBounds = YES;
}
https://stackoverflow.com/a/15489967/9137841 check this it may be help you