An accessibility tip I learned from the Photo Walk Pro blog is a new proofing tool in Photoshop CS4 which simulates two types of color blindness (or color deficient view).
The simple how to is that you:
1. Open an image in Photoshop CS4.
2. Go to the View menu then Proof Setup then select one of the two Color Blindness options at the bottom of the menu. See Photo Walk Pro entry for screencaps.
3. To return to full color, go to View then Proof Colors.
If successful, the colors of your image will be reduced to just those seen by certain types of color deficient viewers – essentially shades or royal blue and yellow/brown. The two spectra images below are a simple demo.
|Normal Vision||Color Deficient|
Besides showing you what a color blind user may see, this proofing tool is a chance to see if your informational graphics are coherent to a color deficient user. For example when the color coded labels of the fake K-12 site are proofed in a color deficient proof, almost all the changes in hue are lost and replaced with varying shades of olive brown.
Fortunately, the value contrast is sufficient that the labels can be read…even if the student might be confused with the instructions “Click the red one.”
Full Color K-12 Labels
Color Deficient Version
I should point out that there are lots of variations among color deficient viewers, especially in terms of how red is perceived – I’ve seen reports that red = black or that red = brown. It is a clear demonstration of why many color deficient users fail to understand the excitement of autumn leaf colors or can’t tell blue and purple apart.