Black? Red? Grey? Squirrel

My kitchen has a large window overlooking the backyard so I am often checking for birds and squirrels out there.   This squirrel was on the feeder at the back but I couldn't figure out from the kitchen window why I could see two different colours but could only see one squirrel.   I picked up the camera and went out to get a closer look.   I was amazed - I have never seen a squirrel like this one!   The upper part of his body looks like a black squirrel and rest of him looks like a mix of red and grey squirrel!!  One of the extras also shows the difference in the texture of the fur.   
Has anyone else ever seen anything like this?