The most straightforward way for making sure your colors work well in all appearances (dark, light, increase contrast, and all the combinations) is to use the provided system colors. Check the background and label semantic colors too.
All the info in the Color section of Apple’s Human Interface Guidelines: https://developer.apple.com/design/human-interface-guidelines/color
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If you don't use Color Sets in your Asset Catalog, and you define your color palette in code, you can still check if the user has Increase Contrast enabled to offer a slightly different color that improves the contrast ratio even more. Day 192 (2/2). You can check if the darker system colors is enabled: https://developer.apple.com/documentation/uikit/uiaccessibility/isdarkersystemcolorsenabled Listen to a notification in case this setting changes: https://developer.apple.com/documentation/uikit/uiaccessibility/darkersystemcolorsstatusdidchangenotification And also check if the accessibility contrast is high in your trait collection: https://developer.apple.com/documentation/uikit/uitraitcollection/accessibilitycontrast
Love this feature! Yahoo released the possibility to explore charts with audio, in the finance app, when using screen readers in 2019. You can do now something very similar since iOS 15. https://coolblindtech.com/yahoo-finance-app-makes-charts-accessible-to-blind-and-partially-sighted-users/ You can move your finger in the x-axes, and it will play a sound with a different pitch depending on the data in the y-axes, making it easier to identify trends in the graphs. You need to conform to the AXChart protocol by implementing the accessibilityChartDescriptor property. Documentation: https://developer.apple.com/documentation/accessibility/audio-graphs WWDC21 session: https://developer.apple.com/videos/play/wwdc2021/10122/
Manual testing is crucial. And therefore, reducing friction to let you start your testing process can be a huge help. Selecting some accessibility shortcuts will do that, putting most of iOS' accessibility features at a triple-click of a button.
