Taken from the 2013 Rules...
The colour yellow is prohibited on any players equipment or clothing, except that a player's jersey, pants, gloves or shoes may have yellow, so long as no part of the yellow colouring is more than 0.25 cm from some other colour, and no more than 10% of any 5cm by 5cm square on clothing or item is yellow.
For reference purposes, 'yellow' is any colour similar to Pantone colours 101, 102, 107, 108, 109, 116, 3945, 3955, 3965, and 803, although any head judge may prohibit any equipment they believe interferes with the judges' ability to officiate effectively.
Now read that how you will.... I read it as.. Don't wear yellow... If you do don't complain when a ref runs 20 metres to you because he sees what he thinks is a hit.