The singer, 28, showed off a darker `do as she was dropped off at the posh Mondrian Hotel in West Hollywood Monday.
Before she went to the dark side, Spears had been showing off her trademark blonde locks for months.
Spears has had a successful year with her sell-out global Circus tour and another No. 1 single in October with "Three." She has also been lucky in love -- following a string of Mr. Wrongs -- with agent beau Jason Trawick, 37.