Red, green, and blue
Red, green, and blue are the colours of Wikimedia. The Wikimedia colours keep Wikimedia projects together by linking many brands in a consistent look. See Brand#Using the Wikimedia colors for the specific color values. Even if not all Wikimedia logos are red, green and blue, such as Wikipedia, Wikinews, Wikitionary and etc., most of the logos are still based on these colours.
tool labs (old)
Derived from Community LogoEdit
Unused sister project logo proposalsEdit
Wikimedia Strategic PlanningEdit
From Wikimedia Incubator/logo.
From Wikibooks/Logo/Archive 1.
From Wikidata/Logo voting
More sister project alternativesEdit
Committees, Chapters, Usergroups, WikiProjects, Raccoon LodgesEdit
Why don't we use these colors everywhere?Edit
It was discussed during the 2006 Wiktionary logo vote, and was determined then, that having all the logos use the same color schemes, would be confusing; see example at w:de:Benutzer:Julian~dewiki#Test on logos. See also, these discussions (Discussion on the logo votes#The Color Complication and Talk:Wiktionary/logo/archive-vote-4#Changing colors), in particular this comment: "the only thing we can do is to ensure that newly chosen logos harmonize [with] the others but don't look all the same". See also Logo#Logo guidelines: "It must be substantially different from the other project logos but still harmonize with the others."