Often when taking pictures of pets their fur color can be distorted with flash or not enough quality light. Try to take the picture in natural light, such as outside or by a window during the day.
Make sure the picture is focused on the face and chest of the pet. A good reference photo will show detail in the pets fur, allowing for optimal detail when painting.
Take the photo crouching or laying down to get on the pets level. Get the pet in the center of the photo, for close up shots center the head profile of the pet.