You can try using the tools for designing accessible web sites e.g., CCA
or Accessibility Color Wheel.

http://www.visionaustralia.org.au/info.aspx?page=628
http://gmazzocato.altervista.org/colorwheel/wheel.php

You can pick 2 colors and then see if there is enough color difference and
brightness difference for the 3 most common color defects.  However, it
seems like having individual channels in greyscale as Cam suggested is the
best way to go.  It is rather difficult to find more than 2 colors that
will satisfy everyone because the background is usually grey and that
puts extra constraint in the possible choices.

On Wed, 21 Oct 2009, John Oreopoulos wrote:

> Dear list,
>
> While preparing some confocal imaging results for publication just recently, I
> was informed by one of my PhD committee members that I should try to present
> my multi-dimensional microscopy images in such a way that they are easy to see
> by people who are color blind. Ie: you should choose colors for your single
> monochrome channel images such that when viewed in a merged/overlay image they
> convey the same information as you would see in a standard green/red overlay
> image for colocalization, etc. I've tried to read up a bit on this topic on
> the web and I even searched the confocal listserv archive, but I could find no
> definitive set of rules or guidelines for going about this. The only
> discussion I could find about this on the listserv dates back to 1996 and
> given that imaging has become even more prevalent in today's biological
> sciences since then, I'm wondering if anyone on here now can direct me to a
> good source or set of journal guidelines for publishing color image overlays
> bearing in mind that some of the readers will be color blind . Also, does
> anyone know of any image processing utilities or plugins (ImageJ?) that can
> covert a full color image into a version that is easier to interpret by
> someone who is color blind?
>
> I've come to realize this is even more important than I previously thought
> given that it seems that almost 1 in 10 males worldwide is color blind (the
> occurrence of color blindness is said to be lower in females). Actually, if
> you want to learn more about the topic of how humans perceive color and the
> history of making colors, I highly recommend a BBC documentary I came across
> just yesterday called "Cracking the Colour Code". Very entertaining.
>
> John Oreopoulos
>
> PS: I used both spellings of the word color in the subject line so that others
> can find this thread easily in the future.

-- 
Pang (Wai Pang Chan, [log in to unmask], PAB A087, 206-685-1519)
The Biology Imaging Facility (http://depts.washington.edu/if/)