I wanted to experiment with Ignacio Paz Posse's snippet for colouring the mode line of the active window ever so slightly different to make it easier to see where the active window is. I usually have global-hl-line-mode turned on, so that highlight is another indicator, but let's see how this tweak feels. I modified the code so that it uses the theme colours from the currently-selected Modus themes, since I trust Prot's colour choices more than I trust mine. Thanks to Irreal for sharing Ignacio's comment!

(defun my-update-active-mode-line-colors ()
  (set-face-attribute
   'mode-line nil
   :foreground (modus-themes-get-color-value 'fg-mode-line-active)
   :background (modus-themes-get-color-value 'bg-blue-subtle)))
(use-package modus-themes
  :hook
  (modus-themes-after-load-theme . my-update-active-mode-line-colors))