NSPopover + NSBox in dark mode tint/gamma issue

Question

I have NSPopover with NSBox and subviews are: MKMapView and NSImageView. In dark mode the whole NSBox adds gamma/tint to all subviews. This doesn't appear in light mode (compare images below). It seems to be something with NSVisualEffectView. How can I prevent/disable this effect?

PS: This effect doesn't show in normal window. Only popover is affected.

Code out of the box drag&drop elements. Mojave 10.14.4

- (IBAction)showPopover:(id)sender {
    [[self popover] showRelativeToRect:[sender bounds] ofView:sender preferredEdge:NSRectEdgeMaxX];
}

Edit: APR2020 According to "Adopting advanced features of the new ui of os x yosemite" (youtube) this happens because of some vibrancy effect of the fill color. Popover has effective appearance of NSVibrantDarkAppearance

(lldb) po [self.view .effectiveAppearance]
▿ 1 element
  - 0 : <NSCompositeAppearance: 0x60000210a940
 (
    "<NSVibrantDarkAppearance: 0x60000170b840>",
    "<NSDarkAquaAppearance: 0x60000170ae80>",
    "<NSSystemAppearance: 0x60000170afc0>"
)>
lldb) po [self.view .superview]
▿ 1 element
  ▿ 0 : Optional<NSView>
    - some : <NSPopoverFrame: 0x1020a63f0; material: Popover; blendingMode: BehindWindow; state: Active>

So other possible solution is to use fill color which is not vibrant.

Answer 1

Solved by adding extra NSVisualEffectView behind the NSBox where blending is set to happen within window. left(with visual effect view), right (without).