Milo knows his colours, and has done since about 12 months old.

how does Yasin go with red-green, does he get those two mixed up. I think red-green is the most common form or colourblindness, but there are more than one kind.

There should be some free tests online, or in books a the library (science geek here, I used to look this stuff up all the time) that have the colour blind test, and there will be a word or a picture that only people who are colourblind can see properly. Printed tests in a book will be better than something online becuase of the changed in colour/resolutione etc.

If you google colour blindness on google australia, the first link is to SA CYH and has some really good info there.