Styling a search bar is hard. Lots of developers opt to build their own instead. If you do, remember to add the .searchField accessibility trait. VoiceOver will announce "Search Field" indicating the user that results might change as they type.
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An interesting speech attribute for attributed accessibility labels is accessibilitySpeechIPANotation that lets you specify how VoiceOver should pronounce a label with the International Phonetic Alphabet (IPA) notation. https://developer.apple.com/documentation/foundation/nsattributedstring/key/accessibilityspeechipanotation
@azzoor has this great video with some advice on how to set up your device for testing accessibility and a ton of tips will get you testing effectively in no time. https://m.youtube.com/watch?v=Ca1H6wF348g&feature=youtu.be
Color contrast between text and background is very important for perceivability. As colors come closer to each other, they’re more difficult to distinguish. Notice that colors that work well with big font sizes may not for smaller text.
