Sometimes it won't be enough to make colors darker or lighter for Increase Contrast. As always, it is important to do some testing. The same colors might be used with different backgrounds or text colors and the contrast could actually get worse.
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iOS and Xcode provide a wide variety of tools and options to deal with color contrast ratios. From system colors, that automatically support Increase Contrast, to high contrast color and asset variants, and even a built-in contrast calculator.
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.
Touch target sizes are recommended to be at least 44 x 44 points. Buttons in the navigation bar ( especially when not using nav bar button items), dismiss buttons, and custom toolbars, are use cases that tend to have smaller sizes.
