The best way for me to see your pet's true fur colour, is with natural daylight. When a house light is on for example, it can make the fur appear to have a funny tinted colour. Try and let in as much natural light as you can, or you can even take your pet's photo outside (if possible).
Again, try to avoid direct sunlight on your pet. As this can have the same effect and change the colour of your pet's fur.