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10. 顏色與排版（Color and Typography）
10.1 顏色加強交流（Color Enhances Communication）
In iOS, color helps indicate interactivity, impart vitality, and provide visual continuity. The built-in apps use a family of pure, clean colors that look great individually and in combination, and on both light and dark backgrounds.
在 iOS 中，顏色有助于表達交互性、透露活力，也提供了可視化的連續性。內置 app 使用一系列無論單看還是組合都看上去不錯的、純粹干凈的顏色，而且這些顏色無論背景明暗都有較好效果。
If you create multiple custom colors, make sure they work well together.?For example, if pastels are essential to your app’s style, you should create a family of coordinating pastels that can be used throughout the app.
如果創建多種自定義顏色，那一定要保證它們搭配得很好。例如，如果 app 的風格是輕柔的彩色，那就應該創建一系列協調搭配的彩色并在 app 中使用。
Pay attention to color contrast in different contexts.?For example, if there’s not enough contrast between the navigation bar background and the bar-button titles, the buttons will be hard for users to see. A quick but unscientific way to find out if your colors have sufficient contrast is to view your app on a device in different lighting conditions, including outdoors on a sunny day.
注意在不同環境下使顏色有差異。例如，如果導航欄背景和上面的按鈕標題顏色差異不夠明顯，那用戶就很難看到按鈕。有一種快速但不夠科學的方法來驗證顏色是否有足夠的差異性，那就是在一個不同的光線條件下的設備里查看 app，包括陽光明媚時的戶外。
Although viewing your app on a device can help you find some of the areas you need to work on, it's no substitute for a more objective approach that yields reliable results. This approach involves determining the ratio between the luminance values of the foreground and background colors. To get this ratio, use an online contrast ratio calculator or you can perform the calculation yourself using the formula established in the WCAG 2.0 standard. Ideally the color contrast ratio in your app is 4.5:1 or higher.
雖然這種方法有助于發現那些有待繼續改進的區域，但它還是不能替代一個獲得可靠結果的更客觀的方法。這個方法涉及到前景色與背景色亮度值間的比例如何。為了獲得這一比例，使用在線差異率計算器或者使用基于 WCAG 2.0 標準的公式自己計算。理想情況下，顏色差異率應該為 4.5：1 或者更高。
Take bar translucency and app content into account when you use a custom bar tint.?If you need to create a bar tint that matches a specific color, such as a color in an existing brand, you may have to experiment with various colors before you get the results you want. A bar’s appearance is affected by both the translucency that iOS provides and the appearance of the app content that can be behind the bar.
使用自定義欄提示的時候，要考慮欄的透明度和 app 內容。如果需要創建欄提示來匹配一個特定顏色，例如一個已存在的品牌的顏色，那需要在獲得滿意效果前進行多種顏色的驗證。欄的外觀同時受 iOS 提供的透明度和欄下面的 app 內容顯示兩個因素的影響。
后一篇：iOS 8人機交互指南（11）
