In 10,000 yrs, barring human interference, what kinds of evolution might we expect in familiar animals? Leaving aside the causes of the adaptation, for example, is it possible that the grey squirrel could evolve into a jet-black squirrel? Is it possible that a raven or a vulture could increase in size to be twice as big as before?
The example to look to is dogs.
Humans did interfere, but not via genetic manipulation. They simply selected for the dogs which fit the criteria they wanted. 10,000 years has produced the range of sizes and shapes dogs have today. But there have not been flying dogs, or photosynthetic dogs. Your example of color differences and size difference falls well within the range of what has happened with dogs.
Arguably environmental circumstances would produce evolution more slowly than artificial selection but not necessarily so. If twice as many black squirrels make it to reproductive age as any other color squirrel, it will be all black squirrels very quickly.
Without environmental changes, one would expect no evolutionary changes at all. Indeed, throughout biological history most species have stayed relatively stable, with tiny, slow changes, for hundreds of thousands of years. Hundreds of millions, in the case of species like sharks.
On the other hand, if you are supposing some kind of major environmental change -- the sudden absence of humans, for example -- then minor changes (like coloration) can happen in a dozen generations, and major changes can happen in a few hundred. Given that 10,000 years is 10,000 squirrel generations, for example, says that you would expect at least minor changes in coat and coloration among squirrels, and substantial changes in appearance with any environmental change.