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
You may also find interesting...
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
When implementing a UISlider, it is a good idea to consider how much the slider value should change when swiping up/down to adjust it. It might not always make sense to do it in 10% increments, which is the default behaviour. Could be because the value at those intervals doesn't make sense, or feel random, or because it wouldn't provide the user with a fine enough control being able to go through the whole slider in just 10 swipes. It user will still be able to adjust the slider to any value by double tapping and holding and then moving the finger left or right, bypassing VoiceOver gestures. VoiceOver announces the new value as it changes.
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/
