Like size, color is not a good indicator of the type of bear.
The "black bear" can come in many shades, from nearly blond, to cinnamon, to black. A female can even have a litter with several different colored cubs.
The term "grizzly" bear comes from the lighter colored tips of the hair, giving the bear a grizzled or silvertip look. This "look" can be used in addition to other features to help identify a bear, but grizzly bears can be anywhere from a light tan to a very dark, almost black color.
Do not use color alone to determine the type of bear you are looking at.