The Tigers wear the orange neckerchief and hat with the blue Class A uniform to the Go Sees and Pack Meetings. In our Pack, the tigers wear the orange tee shirt to den meetings or go sees. Just depends on what is happening.
The boys in my den only wore the orange t'shirt to summer camp and pack campouts. They usually wore the blue shirt with orange neckerchief and tiger slide, tiger hat, and socks. This year they are wolves and wear the gold and next year as bears it'll be light blue and as webelos will be plaid neckerchiefs.
We really hardly ever wore our orange shirts. Just depends on the pack I guess too.
BSA regulations state that the orange shirt is not the official Tiger Cub uniform since 2002. The orange shirts have been slowly weeded out; they can be used as a Class B activity shirt but are not allowed to be considered as the Tiger Cub uniform. They wear the blue uniform up to Webelos; I suggest purchasing the shirt rather large for the boy to grow into - he has at least three if not four years to wear it. Or better yet, start a uniform bank in your pack for the 'gently used' hand-me-downs that the boys out-grow or graduate out of the pack.