You should convey important information in multiple modes, not just color. If you are still required to do so, at the very least you should complement that info with other modes, like symbols, if the user requested differentiation without color.
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You can add an observer to listen for changes in the content size category, in case it is more convenient than overriding traitCollectionDidChange(_:).
Guidelines from Apple: Begin with a verb that explains the results of the action. Avoid using the imperative form of a verb because that can make it sound like a command. Don’t include the action type. Don’t include the control. https://developer.apple.com/documentation/objectivec/nsobject-swift.class/accessibilityhint
Images can automatically scale for accessibility content size categories, by setting the adjustsImageSizeForAccessibilityContentSizeCategory property to true, for any UIImageView you'd like to get its size adjusted. https://developer.apple.com/documentation/uikit/uiaccessibilitycontentsizecategoryimageadjusting/adjustsimagesizeforaccessibilitycontentsizecategory
