Some organizations use color coding such as "Green" (for healthy), "Yellow" (for caution), and "Red" (for critical).

有些组织使用彩色编码，比如“Green”(表示健康的)，“Yellow”(表示小心)，以及“Red”(表示危险的)。

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Kaufman's book is a marvel of concision, with a handy color-coding system (red for "medium-size land birds") and a one-page index on the back page.

FORBES: Peterson's Progeny