I wondered how Google AdSense knows when to change the colour of the foreground text so it doesn't become invisible/hard to read, so made a little experiment to try it out myself. It has become a slightly different tool that tells you how readable your text is. Link: http://iron.randombase.com/colorchecker.html DP scores a "perfect" for readability: Foreground: #000000 Background: #E4F5E7 If you think it has completely failed at evaluating your colours, please post them here so I can finetune it a bit .