Color blindness: Are you aware of it? Do you design for it?

Question

I'm curious whether many of us who do design or take design decisions have ever heard of this problem.

I'm aware there are dangerous color combinations, like green + red. This is probably one of the most popular cases of color blindness. If you have green text on a red background and vice versa some people won't see anything.

I've also seen in practice that green text on a blue background was not seen by one guy.

What other color compositions should be avoided, and how often these cases are to be expected?

Let us make some ranging by encounter probability who has the numbers.

Addition: I've just remembered one very bad example that causes problems to just about everyone - blue text on a black background. It's unreadable for all intents and purposes. Never could understand what could possibly compel a web master to use this color combination...

Answer 1

I allways test my pages in http://www.vischeck.com/vischeck/vischeckURL.php to make sure I havent chosen really bad colors. Or this one http://colorfilter.wickline.org/