Srixon has introduced the Z-Star Tour Yellow, which is the same as the existing Z-Star ball except that Srixon claims its yellow colour makes it easier to see. Srixon claims that studies have shown yellow to be the most visible colour in the visual spectrum, and that yellow golf balls are easier to spot from distance than white. Srixon also says that psychological studies have shown that yellow or green colours can have a stress-relieving effect on people, and so the Z-Star Tour Yellow, which is being trialled on Tour by Tim Clark, comes with a greenish tint.