This paper presents an augmented reality-based method to increase human cognitive awareness of the danger/safety in the workspace of a variable impedance actuated (VIA) robot. Specifically, the 'safety aura' around the robot was created using a safety/index defined for each point of the workspace. The safety-index is a composite metric incorporating the measurements of the distance from a point in the workspace to the VIA robot and the corresponding velocity during its motion. The safety aura is task-specific and is able to represent the safety levels in the workspace of the robot as it follows different trajectories. We developed a robot simulator which allows the visualization of the robot's motion and assessment of the corresponding safety aura in 3D space. The generated safety aura was overlaid into mixed reality using Unity 3D platform together with Vuforia and web camera. Simulation results demonstrated the ability of the safety metric based on distance and velocity measurements to qualitatively assess the amount of danger. Our method has the potential to make the physical human robot interaction safer.