Colors override settings are ignored in daemon mode

I'm trying to alter the default background color of modus-operandi to make it yellowish. However, when I use the following statement in my config, the theme is enabled and uses slanted symbols, but my background is white.

I think it might be linked to the fact that I use --daemon mode. My suspicion if strong, because if I remove t parameter from the 'load-theme' and my initial frame is drawn to confirm if I'm sure about lisp code running, everything works well.

However, I don't know how to use customization mechanics in --daemon mode.

  ;; Theme
  (leaf modus-operandi-theme
    :ensure t
    :setq
    (modus-operandi-theme-slanted-constructs . t)
    (modus-operandi-theme-override-colors-alist .
                                                '(("bg-main" . "#fbf8ef")))
    :config
    (load-theme 'modus-operandi t)
    )

My emacs version is:

GNU Emacs 27.0.91 (build 1, x86_64-apple-darwin19.5.0, NS appkit-1894.50 Version 10.15.5 (Build 19F101)) of 2020-07-03