I interviewed last September (hired October) and the invite said business casual. Ties (or polo shirts) are NOT business casual. I wore khaki dress pants, long sleeve button-down dress shirt, and a navy-blue sportcoat. The couple of guys in my group(13) that wore ties took them off pretty quickly, and those that wore an interview suit without the tie still looked more than "business casual."

IF it says business casual, follow the directions! If not, I would go all-out with the traditional interview suit.

Now, about the "Red power tie", .... lol