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http://mandarapte.com/apple/programmatically-change-ios-apps-global-tint-colour-navigation-toolbar-tab-bars-tint-i-e-text-icon-colour-bar-tint-colour-i-e-background-colour-swift-language-developi/
How to programmatically change iOS app’s global tint colour, Navigation / Toolbar / Tab Bar’s tint (i.e. Text & Icon Colour) & bar tint colour (i.e. Background colour) using Swift Language while developing app in Xcode