EDIT: I wouldn't recommend taking these fans apart, your's may be similar to
this guy's
I wouldn't paint fans so valuable
But if you insist: Peel off the sticker on the back and pop off the lock ring. Fan blades should come of with ease. If there is no ring then you may just have to pop off the blades
like this.
If I were you, I wouldn't paint the fan blades themselves, only the fan housing. Any misbalence of weight can cause degredation in performance and longetivity as the default surface is designed to direct the airflow. The presence of paint thickening the blades may interfere.