Is my roommate colorblind?!
Question: Is my roommate colorblind?
Answers:
Colour blind is a misnomer, colour defective would be a better term. Those with colour vision defects still see colours and can often name them correctly. They see hundreds of different colours instead of thousands.
If your friend fails the Ishihara test, then he has a colour defect.
I'm an optometrist
The Ishihara Colour test checks for colour anomalies... (ie. deviations from the norm). And it only specifically tests for GENETIC colour vision problems (Red-Green or Blue-Green deficiencies). As such, it uses 'pure' colours... ie, reds are made of pure reds, and greens made up of pure greens. So a person with colour vision anomalies will have difficulty differentiating between the pure colours in the Ishihara plates.
Now for everyday colours.. like clothing, signs.. they are not PURE colours, but mixtures of nimiscule pigment spots.. (think of your ink-jet printer..) So although they can't differentiate Red-Green or Blue-Green.. they may be able to pick up the other colours mixed in with the 'everyday' reds and greens (eg, leaves, fruit, ocean water... etc).... and learn what is red/green/blue..
However, if they are ever exposed to pure colours... like those used in the DEFENCE FORCE, or with ELECTRICAL WIRING... they may get the confused just like the Ishihara plates.
It's possible that there is something wrong with his retina which is causing him problems during the Ishihara plate test. Also, he would need to be tested through all the plates, not just a few.
Show him something red or green, and tell him to tell you what color it is. If he knows the color, then he's not color blind