Color management is enabled by default for new scenes, and saved on a scene-by-scene basis. To enable or disable color management for the current scene, toggle Enable Color Management in the Color Management preferences.
Note that activating color management automatically enables Floating Point Render Target for Viewport 2.0, and sets Format to R32G32B32A32_FLOAT. You can change these settings if you experience performance problems with older graphics cards, but then you may see color clipping, banding, and other artifacts in the viewport. In addition, using the Eyedropper tool to pick colors in the viewport may result in incorrect color values.