bleh

These are the only possible colors they could've seen: 
A => R&Y or R&G or Y&Y 
B => Y&G or G&G 
C => Y&G or G&G 
 
Since B and C didnt see Red, we have our 1st CLUE: 
1.) A's tie isnt Red. 
 
From there we can deduce... 
If A isnt Red and B and C didnt see Red, then 
2nd CLUE: 
2.) None of them wears Red 
 
So, we can forget the colors containing Red. (written above ^ there)  
A => YY 
3rd CLUE: 
3) Both B and C should be Yellow. 
 
And statement B&C says one of them is Green. 
That could only be A's Tie. 
 
ANSWER: 
Alan = GREEN 
Bert = YELLOW 
Callum = YELLOW 
Tadaaa!  
 
O_x

bleh