If you have been to Darwin Station in Puerto Ayora, then this attraction really does not provide much more interest. The main difference that I understood was a different type of large land tortoise, i.e., Cerro has saddle back and Darwin has dome but larger tortoises. I am sure to the purest there are more differences. Darwin had a few land iguanas and Cerro Colorado is more of a nature trail that provides some plaques about the certain trees. Both places have about the same amount of turtles and both bread tortoises for eventual release in the wild. These are not park guided tours or interactive, so if you do not have a guide, it could be very limited about what you learn.
From the main land you can fly to either San Christobal (Cerro) or Santa Cruz (Darwin) so if not part of your boat agenda it is worth the time for what ever island you come in on. If you fly into Santa Cruz, you should seriously consider a short drive away, about 20 minutes or $12 per hour for a taxi, the Reserva El Chato and for $3 USD per person see many many tortoises in a natural setting and get as close as two meters to them (there is no barrier you are just supposed to stay two meters away. On the way you should see turtles along the road that are just roaming in the wild The lava tunnels are close by and so are the craters. But in my opinion if you want to see the larger tortoises in a natural setting, El Chato is the place to go.