update terminology: color blind (#2143)

w3c/low-vision-a11y-tf#121 (comment)

w3c/low-vision-a11y-tf#121 (comment)

---------

Co-authored-by: Kenneth G. Franqueiro <[email protected]>
Co-authored-by: Mike Gower <[email protected]>

Author: 3 people

understanding/20/use-of-color.html

@@ -135,8 +135,8 @@ <h2>Benefits of Use of Color</h2>
 
          <li>Some older users may not be able to see color well.</li>
 
-         <li>Users who have color-blindness benefit when information conveyed by color is available
-            in other visual ways.
+         <li>Users who cannot distinguish between certain colors (often called “color blindness”)
+            benefit when information conveyed by color is available in other visual ways.
          </li>
 
          <li>People using limited color monochrome displays may be unable to access