The green and red colors have two background versions. The green-bg and red-bg are normal light background colors. The green-bg-s, red-bg-s, and blue-bg-s are a stronger version and are used in ediff and places were text is added, deleted or changed.
Since the ediff background colors were changed to not use the
...-bg-s
colors, the following paragraph in: https://github.com/nashamri/spacemacs-theme#override-themes-colors probably needs to be rewritten/removed.