Traditionally, printer makers have charged big corporate customers a per-page fee for printing services: up to 8 cents a page for a color document and less than 2 cents a page for black-and-white.
An easy way to check your colors and contrast is to print your portlet's output on a black-and-white printer and give it to someone else.
检查颜色和对比度的简单方法是将portlet的输出通过到黑白打印机打印，并拿给其他人看。
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If you have a monochrome printer or you do not want to waste expensive color ink cartridges, turn off "print in color" to print black text without any background colors.