NSVisualEffectView change takes more than one click to change

So I have an NSVisualEffectView hooked up with a button and some icons. The material of this view is originally equal to NSVisualEffectMaterialDark in other words, Vibrant Dark.

The following code I wrote is supposed to do the following:

1) Detect if the view's material is NSVisualEffectMaterialDark or NSVisualEffectMaterialLight
2) Change the BOOL isDark to YES/NO respectively
3) Change the view's appearance, in other words the material, from Dark to Light / Light to Dark based on the current view.

The problem is that when I run the app and click the button, NSVisualEffectView's colour changes from a saturated dark to a less one, and not Light as it is supposed to.

What can I do to fix this problem and prevent it from happening?

Note: the NSVisualEffectView's name is sideBar, the button's name is lightButton and isDark is originally set to YES.

Here is my code:

    -(IBAction)toggleLighting:(id)sender{
    if (self.sideBar.material == NSVisualEffectMaterialDark){
        _lightButton.title = (@"Dark Mode");
        [_lightButton setImage:[NSImage imageNamed:@"Dark Mode Icon"]];
        [_lightButton setAlternateImage:[NSImage imageNamed:@"Dark Mode Icon (Alt)"]];
        isDark = YES;
        NSLog(@"Changed to Light Theme");
    } else if (self.sideBar.material == NSVisualEffectMaterialLight){
        _lightButton.title = (@"Light Mode");
        [_lightButton setImage:[NSImage imageNamed:@"Light Mode Icon"]];
        [_lightButton setAlternateImage:[NSImage imageNamed:@"Light Mode Icon (Alt)"]];
        isDark = NO;
        NSLog(@"Changed to Dark Theme");
    }

    if (isDark==YES){
        _sideBar.material = NSVisualEffectMaterialLight;
        isDark = NO;
    } else if (isDark==NO) {
        _sideBar.material = NSVisualEffectMaterialDark;
        isDark = YES;
    }
}

It turns out that the code I wrote is a little problematic, as expected of course. The NSVisualEffectView has none of the above material it checks for, NSVisualEffectMaterialDark nor NSVisualEffectMaterialLight, therefore both conditions are false. It seems that it chooses to set the material to a different type of dark so that the materials will finally match and be able to compare them properly.

By stating either material (NSVisualEffectMaterialDark nor NSVisualEffectMaterialLight), in - (void)applicationDidFinishLaunching:(NSNotification *)aNotification I was able to fix the issue where I had to click twice for the button to actually work.

EDIT:

It turns out there are other materials I wasn't aware of and they happened to be the desired ones.
These are NSVisualEffectMaterialMediumLight and NSVisualEffectMaterialUltraDark.