Yellow means you have Wiiconnect24 on and the system is in standby mode, meaning it is able to accept Wiimail and keep the various channels updated with new info as required, although it seems to me that the channels really don't update till you access them.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70