For a RED/YELLOW map:
This is caused by the Terrain Overlay. In Plan Mode, your map will be tinted to show terrain based on your highest planned cruise altitude (if you haven’t set an altitude, everything will be tinted red). In Fly Mode, the map is tinted according to your current GPS altitude. Terrain within 1500′ to 500′ will be tinted yellow, whereas terrain 501′ to above will be tinted red.
Above is an example of the terrain overly when in planning mode.
Tap En Route to view your map.
Tap the Map Settings button (two gears icon, top right corner of screen)
Un-tick Terrain Overlay
Your map should return to normal
For an Orange/Blue/Purple map:
This is caused by a SIGMET that is current over your viewing area that may have not been active the last time you viewed it. Orange is for Turbulence. Blue is for Icing.
Tap En Route to view your map.
Tap the Weather Overlays button (RADAR icon, near the top right corner of screen)
Un-tick SIGMETs
Your map should return to normal
Above is an example of both Severe Turbulence and Icing SIGMETs over eastern Australia